10 files changed, 195 insertions, 140 deletions

diff --git a/spec/ruby/core/io/shared/binwrite.rb b/spec/ruby/core/io/shared/binwrite.rb
index 3649bb47ff..64793b1936 100644
--- a/spec/ruby/core/io/shared/binwrite.rb
+++ b/spec/ruby/core/io/shared/binwrite.rb
@@ -21,6 +21,14 @@ 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(ArgumentError, "wrong number of arguments (given 4, expected 2..3)")
+  end
+
   it "creates a file if missing" do
     fn = @filename + "xxx"
     begin
@@ -67,8 +75,13 @@ 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)
+    -> { IO.send(@method, @filename, "abcde", mode: "r") }.should.raise(IOError)
   end
 
   it "truncates if empty :opts provided and offset skipped" do
diff --git a/spec/ruby/core/io/shared/chars.rb b/spec/ruby/core/io/shared/chars.rb
index 266566f221..efd4d5ee10 100644
--- a/spec/ruby/core/io/shared/chars.rb
+++ b/spec/ruby/core/io/shared/chars.rb
@@ -24,7 +24,7 @@ describe :io_chars, shared: true do
   describe "when no block is given" do
     it "returns an Enumerator" do
       enum = @io.send(@method)
-      enum.should be_an_instance_of(Enumerator)
+      enum.should.instance_of?(Enumerator)
       enum.first(5).should == ["V", "o", "i", "c", "i"]
     end
 
@@ -38,19 +38,19 @@ describe :io_chars, shared: true do
   end
 
   it "returns itself" do
-    @io.send(@method) { |c| }.should equal(@io)
+    @io.send(@method) { |c| }.should.equal?(@io)
   end
 
   it "returns an enumerator for a closed stream" do
-    IOSpecs.closed_io.send(@method).should be_an_instance_of(Enumerator)
+    IOSpecs.closed_io.send(@method).should.instance_of?(Enumerator)
   end
 
   it "raises an IOError when an enumerator created on a closed stream is accessed" do
-    -> { IOSpecs.closed_io.send(@method).first }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send(@method).first }.should.raise(IOError)
   end
 
   it "raises IOError on closed stream" do
-    -> { IOSpecs.closed_io.send(@method) {} }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send(@method) {} }.should.raise(IOError)
   end
 end
 
diff --git a/spec/ruby/core/io/shared/codepoints.rb b/spec/ruby/core/io/shared/codepoints.rb
index 6872846c1a..21c756986f 100644
--- a/spec/ruby/core/io/shared/codepoints.rb
+++ b/spec/ruby/core/io/shared/codepoints.rb
@@ -13,7 +13,7 @@ describe :io_codepoints, shared: true do
 
   describe "when no block is given" do
     it "returns an Enumerator" do
-      @enum.should be_an_instance_of(Enumerator)
+      @enum.should.instance_of?(Enumerator)
     end
 
     describe "returned Enumerator" do
@@ -39,7 +39,7 @@ describe :io_codepoints, shared: true do
 
   it "raises an error if reading invalid sequence" do
     @io.pos = 60  # inside of a multibyte sequence
-    -> { @enum.first }.should raise_error(ArgumentError)
+    -> { @enum.first }.should.raise(ArgumentError)
   end
 
   it "does not change $_" do
@@ -49,6 +49,6 @@ describe :io_codepoints, shared: true do
   end
 
   it "raises an IOError when self is not readable" do
-    -> { IOSpecs.closed_io.send(@method).to_a }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send(@method).to_a }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/core/io/shared/each.rb b/spec/ruby/core/io/shared/each.rb
index 02bbe19c1a..ae60c3506a 100644
--- a/spec/ruby/core/io/shared/each.rb
+++ b/spec/ruby/core/io/shared/each.rb
@@ -24,7 +24,7 @@ describe :io_each, shared: true do
     end
 
     it "returns self" do
-      @io.send(@method) { |l| l }.should equal(@io)
+      @io.send(@method) { |l| l }.should.equal?(@io)
     end
 
     it "does not change $_" do
@@ -33,12 +33,8 @@ 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)
+      -> { IOSpecs.closed_io.send(@method) {} }.should.raise(IOError)
     end
 
     it "makes line count accessible via lineno" do
@@ -54,7 +50,7 @@ describe :io_each, shared: true do
     describe "when no block is given" do
       it "returns an Enumerator" do
         enum = @io.send(@method)
-        enum.should be_an_instance_of(Enumerator)
+        enum.should.instance_of?(Enumerator)
 
         enum.each { |l| ScratchPad << l }
         ScratchPad.recorded.should == IOSpecs.lines
@@ -74,12 +70,12 @@ describe :io_each, shared: true do
     describe "when limit is 0" do
       it "raises an ArgumentError" do
         # must pass block so Enumerator is evaluated and raises
-        -> { @io.send(@method, 0){} }.should raise_error(ArgumentError)
+        -> { @io.send(@method, 0){} }.should.raise(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)
+      -> { @io.send(@method, 2**128){} }.should.raise(RangeError)
     end
   end
 
@@ -130,7 +126,7 @@ describe :io_each, shared: true do
     describe "when no block is given" do
       it "returns an Enumerator" do
         enum = @io.send(@method, nil, 1024)
-        enum.should be_an_instance_of(Enumerator)
+        enum.should.instance_of?(Enumerator)
 
         enum.each { |l| ScratchPad << l }
         ScratchPad.recorded.should == [IOSpecs.lines.join]
@@ -147,7 +143,7 @@ describe :io_each, shared: true do
 
     describe "when a block is given" do
       it "accepts an empty block" do
-        @io.send(@method, nil, 1024) {}.should equal(@io)
+        @io.send(@method, nil, 1024) {}.should.equal?(@io)
       end
 
       describe "when passed nil as a separator" do
@@ -180,16 +176,14 @@ describe :io_each, shared: true do
       ScratchPad.recorded.should == IOSpecs.lines_without_newline_characters
     end
 
-    ruby_version_is "3.0" do
-      it "raises exception when options passed as Hash" do
-        -> {
-          @io.send(@method, { chomp: true }) { |s| }
-        }.should raise_error(TypeError)
+    it "raises exception when options passed as Hash" do
+      -> {
+        @io.send(@method, { chomp: true }) { |s| }
+      }.should.raise(TypeError)
 
-        -> {
-          @io.send(@method, "\n", 1, { chomp: true }) { |s| }
-        }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
-      end
+      -> {
+        @io.send(@method, "\n", 1, { chomp: true }) { |s| }
+      }.should.raise(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
     end
   end
 
@@ -208,20 +202,10 @@ describe :io_each, shared: true do
   end
 
   describe "when passed chomp and nil as a separator" do
-    ruby_version_is "3.2" 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
-
-    ruby_version_is ""..."3.2" do
-      it "yields self's content without trailing new line character" do
-        @io.pos = 100
-        @io.send(@method, nil, chomp: true) { |s| ScratchPad << s }
-        ScratchPad.recorded.should == ["qui a linha cinco.\nHere is line six."]
-      end
+    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
 
@@ -243,7 +227,7 @@ describe :io_each, shared: true do
     it "raises ArgumentError" do
       -> {
         @io.send(@method, "", 1, "excess argument", chomp: true) {}
-      }.should raise_error(ArgumentError)
+      }.should.raise(ArgumentError)
     end
   end
 end
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 7677aada6e..6f318ddee5 100644
--- a/spec/ruby/core/io/shared/new.rb
+++ b/spec/ruby/core/io/shared/new.rb
@@ -1,6 +1,6 @@
 require_relative '../fixtures/classes'
 
-# NOTE: should be syncronized with library/stringio/initialize_spec.rb
+# 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.
@@ -22,7 +22,7 @@ describe :io_new, shared: true do
 
   it "creates an IO instance from an Integer argument" do
     @io = IO.send(@method, @fd, "w")
-    @io.should be_an_instance_of(IO)
+    @io.should.instance_of?(IO)
   end
 
   it "creates an IO instance when STDOUT is closed" do
@@ -32,7 +32,7 @@ describe :io_new, shared: true do
 
       begin
         @io = IO.send(@method, @fd, "w")
-        @io.should be_an_instance_of(IO)
+        @io.should.instance_of?(IO)
       ensure
         STDOUT = stdout
         rm_r stdout_file
@@ -49,7 +49,7 @@ describe :io_new, shared: true do
 
       begin
         @io = IO.send(@method, @fd, "w")
-        @io.should be_an_instance_of(IO)
+        @io.should.instance_of?(IO)
       ensure
         STDERR = stderr
         rm_r stderr_file
@@ -61,7 +61,16 @@ describe :io_new, shared: true 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)
+    @io.should.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(ArgumentError, "wrong number of arguments (given 3, expected 1..2)")
   end
 
   it "accepts a :mode option" do
@@ -199,21 +208,30 @@ describe :io_new, shared: true do
     @io.internal_encoding.to_s.should == 'IBM866'
   end
 
-  ruby_version_is ''...'3.0' do
-    it "accepts nil options" do
-      @io = suppress_keyword_warning do
-        IO.send(@method, @fd, 'w', nil)
-      end
-      @io.write("foo").should == 3
-    end
+  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
 
-  ruby_version_is '3.0' do
-    it "raises ArgumentError for nil options" do
-      -> {
-        IO.send(@method, @fd, 'w', nil)
-      }.should raise_error(ArgumentError)
-    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(ArgumentError)
   end
 
   it "coerces mode with #to_str" do
@@ -296,109 +314,100 @@ describe :io_new_errors, shared: true do
   end
 
   it "raises an Errno::EBADF if the file descriptor is not valid" do
-    -> { IO.send(@method, -1, "w") }.should raise_error(Errno::EBADF)
+    -> { IO.send(@method, -1, "w") }.should.raise(Errno::EBADF)
   end
 
   it "raises an IOError if passed a closed stream" do
-    -> { IO.send(@method, IOSpecs.closed_io.fileno, 'w') }.should raise_error(IOError)
+    -> { IO.send(@method, IOSpecs.closed_io.fileno, 'w') }.should.raise(IOError)
   end
 
   platform_is_not :windows do
     it "raises an Errno::EINVAL if the new mode is not compatible with the descriptor's current mode" do
-      -> { IO.send(@method, @fd, "r") }.should raise_error(Errno::EINVAL)
+      -> { IO.send(@method, @fd, "r") }.should.raise(Errno::EINVAL)
     end
   end
 
   it "raises ArgumentError if passed an empty mode string" do
-    -> { IO.send(@method, @fd, "") }.should raise_error(ArgumentError)
+    -> { IO.send(@method, @fd, "") }.should.raise(ArgumentError)
   end
 
   it "raises an error if passed modes two ways" do
     -> {
       IO.send(@method, @fd, "w", mode: "w")
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
   it "raises an error if passed encodings two ways" do
     -> {
       @io = IO.send(@method, @fd, 'w:ISO-8859-1', encoding: 'ISO-8859-1')
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, 'w:ISO-8859-1', external_encoding: 'ISO-8859-1')
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
+    -> {
+      @io = IO.send(@method, @fd, 'w:ISO-8859-1', internal_encoding: 'ISO-8859-1')
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, 'w:ISO-8859-1:UTF-8', internal_encoding: 'ISO-8859-1')
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
   it "raises an error if passed matching binary/text mode two ways" do
     -> {
       @io = IO.send(@method, @fd, "wb", binmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, "wt", textmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
 
     -> {
       @io = IO.send(@method, @fd, "wb", textmode: false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, "wt", binmode: false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
   it "raises an error if passed conflicting binary/text mode two ways" do
     -> {
       @io = IO.send(@method, @fd, "wb", binmode: false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, "wt", textmode: false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
 
     -> {
       @io = IO.send(@method, @fd, "wb", textmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, "wt", binmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
   it "raises an error when trying to set both binmode and textmode" do
     -> {
       @io = IO.send(@method, @fd, "w", textmode: true, binmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, File::Constants::WRONLY, textmode: true, binmode: true)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
   it "raises ArgumentError if not passed a hash or nil for options" do
     -> {
       @io = IO.send(@method, @fd, 'w', false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, false, false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
     -> {
       @io = IO.send(@method, @fd, nil, false)
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError)
   end
 
-  ruby_version_is ''...'3.0' do
-    it "raises TypeError if passed a hash for mode and nil for options" do
-      -> {
-        suppress_keyword_warning do
-          @io = IO.send(@method, @fd, {mode: 'w'}, nil)
-        end
-      }.should raise_error(TypeError)
-    end
-  end
-
-  ruby_version_is '3.0' 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(ArgumentError)
-    end
+  it "raises ArgumentError if passed a hash for mode and nil for options" do
+    -> {
+      @io = IO.send(@method, @fd, {mode: 'w'}, nil)
+    }.should.raise(ArgumentError)
   end
 end
diff --git a/spec/ruby/core/io/shared/pos.rb b/spec/ruby/core/io/shared/pos.rb
index 3fdd3eb2b3..f4d0405863 100644
--- a/spec/ruby/core/io/shared/pos.rb
+++ b/spec/ruby/core/io/shared/pos.rb
@@ -19,7 +19,7 @@ describe :io_pos, shared: true do
   end
 
   it "raises IOError on closed stream" do
-    -> { IOSpecs.closed_io.send(@method) }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send(@method) }.should.raise(IOError)
   end
 
   it "resets #eof?" do
@@ -62,17 +62,17 @@ describe :io_set_pos, shared: true 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")
+      -> { io.send @method, Object.new }.should.raise(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)
+      -> { io.send @method, 2**128 }.should.raise(RangeError)
     end
   end
 
   it "raises IOError on closed stream" do
-    -> { IOSpecs.closed_io.send @method, 0 }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send @method, 0 }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/core/io/shared/readlines.rb b/spec/ruby/core/io/shared/readlines.rb
index 7681e1b5c1..f54fccc2e3 100644
--- a/spec/ruby/core/io/shared/readlines.rb
+++ b/spec/ruby/core/io/shared/readlines.rb
@@ -1,11 +1,11 @@
 describe :io_readlines, shared: true do
   it "raises TypeError if the first parameter is nil" do
-    -> { IO.send(@method, nil, &@object) }.should raise_error(TypeError)
+    -> { IO.send(@method, nil, &@object) }.should.raise(TypeError)
   end
 
   it "raises an Errno::ENOENT if the file does not exist" do
     name = tmp("nonexistent.txt")
-    -> { IO.send(@method, name, &@object) }.should raise_error(Errno::ENOENT)
+    -> { IO.send(@method, name, &@object) }.should.raise(Errno::ENOENT)
   end
 
   it "yields a single string with entire content when the separator is nil" do
@@ -80,14 +80,12 @@ describe :io_readlines_options_19, shared: true do
       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)
+        -> { IO.send(@method, @name, 2**128, &@object) }.should.raise(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
+      describe "when passed limit" do
+        it "raises ArgumentError when passed 0 as a limit" do
+          -> { IO.send(@method, @name, 0, &@object) }.should.raise(ArgumentError)
         end
       end
     end
@@ -99,18 +97,16 @@ 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 an options Hash" do
-      ruby_version_is "3.0" do
-        it "raises TypeError exception" do
-          -> {
-            IO.send(@method, @name, { chomp: true }, &@object)
-          }.should raise_error(TypeError)
-        end
+      it "raises TypeError exception" do
+        -> {
+          IO.send(@method, @name, { chomp: true }, &@object)
+        }.should.raise(TypeError)
       end
     end
 
@@ -120,7 +116,7 @@ describe :io_readlines_options_19, shared: true do
 
         -> {
           IO.send(@method, @name, obj, &@object)
-        }.should raise_error(TypeError)
+        }.should.raise(TypeError)
       end
     end
   end
@@ -174,17 +170,15 @@ describe :io_readlines_options_19, shared: true do
 
         -> {
           IO.send(@method, @name, " ", obj, &@object)
-        }.should raise_error(TypeError)
+        }.should.raise(TypeError)
       end
     end
 
     describe "when the second object is an options Hash" do
-      ruby_version_is "3.0" do
-        it "raises TypeError exception" do
-          -> {
-            IO.send(@method, @name, "", { chomp: true }, &@object)
-          }.should raise_error(TypeError)
-        end
+      it "raises TypeError exception" do
+        -> {
+          IO.send(@method, @name, "", { chomp: true }, &@object)
+        }.should.raise(TypeError)
       end
     end
   end
@@ -194,7 +188,7 @@ describe :io_readlines_options_19, shared: true do
       it "uses the keyword arguments as options" do
         -> do
           IO.send(@method, @filename, 10, mode: "w", &@object)
-        end.should raise_error(IOError)
+        end.should.raise(IOError)
       end
     end
 
@@ -202,7 +196,7 @@ describe :io_readlines_options_19, shared: true do
       it "uses the keyword arguments as options" do
         -> do
           IO.send(@method, @filename, " ", mode: "w", &@object)
-        end.should raise_error(IOError)
+        end.should.raise(IOError)
       end
     end
 
@@ -213,7 +207,7 @@ describe :io_readlines_options_19, shared: true do
 
         -> do
           IO.send(@method, @filename, sep, mode: "w", &@object)
-        end.should raise_error(IOError)
+        end.should.raise(IOError)
       end
     end
   end
@@ -243,7 +237,7 @@ describe :io_readlines_options_19, shared: true do
     it "uses the keyword arguments as options" do
       -> do
         IO.send(@method, @filename, " ", 10, mode: "w", &@object)
-      end.should raise_error(IOError)
+      end.should.raise(IOError)
     end
 
     describe "when passed chomp, nil as a separator, and a limit" do
diff --git a/spec/ruby/core/io/shared/tty.rb b/spec/ruby/core/io/shared/tty.rb
index 89ac08ec86..1dc0e95739 100644
--- a/spec/ruby/core/io/shared/tty.rb
+++ b/spec/ruby/core/io/shared/tty.rb
@@ -19,6 +19,6 @@ describe :io_tty, shared: true do
   end
 
   it "raises IOError on closed stream" do
-    -> { IOSpecs.closed_io.send @method }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send @method }.should.raise(IOError)
   end
 end
diff --git a/spec/ruby/core/io/shared/write.rb b/spec/ruby/core/io/shared/write.rb
index 9503f94212..5de9fe4335 100644
--- a/spec/ruby/core/io/shared/write.rb
+++ b/spec/ruby/core/io/shared/write.rb
@@ -23,7 +23,7 @@ describe :io_write, shared: true do
   end
 
   it "checks if the file is writable if writing more than zero bytes" do
-    -> { @readonly_file.send(@method, "abcde") }.should raise_error(IOError)
+    -> { @readonly_file.send(@method, "abcde") }.should.raise(IOError)
   end
 
   it "returns the number of bytes written" do
@@ -66,7 +66,7 @@ describe :io_write, shared: true do
   end
 
   it "raises IOError on closed stream" do
-    -> { IOSpecs.closed_io.send(@method, "hello") }.should raise_error(IOError)
+    -> { IOSpecs.closed_io.send(@method, "hello") }.should.raise(IOError)
   end
 
   describe "on a pipe" do
@@ -85,15 +85,70 @@ 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/)
+        -> { @w.send(@method, "foo") }.should.raise(Errno::EPIPE, /Broken pipe/)
       end
     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(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