Merge rubygems master from upstream.

  I picked the commit from 3c469e0da538428a0ddd94f99aa73c32da22e8ba

55 files changed, 1024 insertions, 1026 deletions

diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 193e8d3539..c013e4b8ed 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -670,6 +670,21 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
     index
   end
 
+  ##
+  # Add a list of paths to the $LOAD_PATH at the proper place.
+
+  def self.add_to_load_path(*paths)
+    insert_index = load_path_insert_index
+
+    if insert_index
+      # gem directories must come after -I and ENV['RUBYLIB']
+      $LOAD_PATH.insert(insert_index, *paths)
+    else
+      # we are probably testing in core, -I and RUBYLIB don't apply
+      $LOAD_PATH.unshift(*paths)
+    end
+  end
+
   @yaml_loaded = false
 
   ##
@@ -1084,6 +1099,13 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
   end
 
   ##
+  # Is this a java platform?
+
+  def self.java_platform?
+    RUBY_PLATFORM == "java"
+  end
+
+  ##
   # Load +plugins+ as Ruby files
 
   def self.load_plugin_files(plugins) # :nodoc:
@@ -1243,7 +1265,7 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
     #
 
     def register_default_spec(spec)
-      new_format = Gem.default_gems_use_full_paths? || spec.require_paths.any? {|path| spec.files.any? {|f| f.start_with? path } }
+      new_format = spec.require_paths.any? {|path| spec.files.any? {|f| f.start_with? path } }
 
       if new_format
         prefix_group = spec.require_paths.map {|f| f + "/"}.join("|")
diff --git a/lib/rubygems/commands/pristine_command.rb b/lib/rubygems/commands/pristine_command.rb
index a25b690afc..e4628bdd40 100644
--- a/lib/rubygems/commands/pristine_command.rb
+++ b/lib/rubygems/commands/pristine_command.rb
@@ -104,7 +104,7 @@ extensions will be restored.
               end.flatten
             end
 
-    specs = specs.select{|spec| RUBY_ENGINE == spec.platform || Gem::Platform.local === spec.platform }
+    specs = specs.select{|spec| RUBY_ENGINE == spec.platform || Gem::Platform.local === spec.platform || spec.platform == Gem::Platform::RUBY }
 
     if specs.to_a.empty?
       raise Gem::Exception,
diff --git a/lib/rubygems/commands/query_command.rb b/lib/rubygems/commands/query_command.rb
index 5a42d45249..4fb23bc6c1 100644
--- a/lib/rubygems/commands/query_command.rb
+++ b/lib/rubygems/commands/query_command.rb
@@ -78,46 +78,58 @@ is too hard to use.
   end
 
   def execute
+    gem_names = Array(options[:name])
+
+    if !args.empty?
+      gem_names = options[:exact] ? args.map{|arg| /\A#{Regexp.escape(arg)}\Z/ } : args.map{|arg| /#{arg}/i }
+    end
+
+    terminate_interaction(check_installed_gems(gem_names)) if check_installed_gems?
+
+    gem_names.each { |n| show_gems(n) }
+  end
+
+  private
+
+  def check_installed_gems(gem_names)
     exit_code = 0
-    if options[:args].to_a.empty? and options[:name].source.empty?
-      name = options[:name]
-      no_name = true
-    elsif !options[:name].source.empty?
-      name = Array(options[:name])
+
+    if args.empty? && !gem_name?
+      alert_error "You must specify a gem name"
+      exit_code = 4
+    elsif gem_names.count > 1
+      alert_error "You must specify only ONE gem!"
+      exit_code = 4
     else
-      args = options[:args].to_a
-      name = options[:exact] ? args.map{|arg| /\A#{Regexp.escape(arg)}\Z/ } : args.map{|arg| /#{arg}/i }
+      installed = installed?(gem_names.first, options[:version])
+      installed = !installed unless options[:installed]
+
+      say(installed)
+      exit_code = 1 if !installed
     end
 
-    prerelease = options[:prerelease]
+    exit_code
+  end
 
-    unless options[:installed].nil?
-      if no_name
-        alert_error "You must specify a gem name"
-        exit_code |= 4
-      elsif name.count > 1
-        alert_error "You must specify only ONE gem!"
-        exit_code |= 4
-      else
-        installed = installed? name.first, options[:version]
-        installed = !installed unless options[:installed]
+  def check_installed_gems?
+    !options[:installed].nil?
+  end
 
-        if installed
-          say "true"
-        else
-          say "false"
-          exit_code |= 1
-        end
-      end
+  def gem_name?
+    !options[:name].source.empty?
+  end
 
-      terminate_interaction exit_code
-    end
+  def prerelease
+    options[:prerelease]
+  end
 
-    names = Array(name)
-    names.each { |n| show_gems n, prerelease }
+  def show_prereleases?
+    prerelease.nil? || prerelease
   end
 
-  private
+  def args
+    options[:args].to_a
+  end
 
   def display_header(type)
     if (ui.outs.tty? and Gem.configuration.verbose) or both?
@@ -128,56 +140,57 @@ is too hard to use.
   end
 
   #Guts of original execute
-  def show_gems(name, prerelease)
-    req = Gem::Requirement.default
-    # TODO: deprecate for real
+  def show_gems(name)
+    show_local_gems(name)  if local?
+    show_remote_gems(name) if remote?
+  end
+
+  def show_local_gems(name, req = Gem::Requirement.default)
+    display_header("LOCAL")
+
+    specs = Gem::Specification.find_all do |s|
+      s.name =~ name and req =~ s.version
+    end
+
     dep = Gem::Deprecate.skip_during { Gem::Dependency.new name, req }
-    dep.prerelease = prerelease
+    specs.select! do |s|
+      dep.match?(s.name, s.version, show_prereleases?)
+    end
 
-    if local?
-      if prerelease and not both?
-        alert_warning "prereleases are always shown locally"
-      end
+    spec_tuples = specs.map do |spec|
+      [spec.name_tuple, spec]
+    end
+
+    output_query_results(spec_tuples)
+  end
 
-      display_header 'LOCAL'
+  def show_remote_gems(name)
+    display_header("REMOTE")
 
-      specs = Gem::Specification.find_all do |s|
-        s.name =~ name and req =~ s.version
-      end
+    fetcher = Gem::SpecFetcher.fetcher
 
-      spec_tuples = specs.map do |spec|
-        [spec.name_tuple, spec]
-      end
+    spec_tuples = if name.respond_to?(:source) && name.source.empty?
+                    fetcher.detect(specs_type) { true }
+                  else
+                    fetcher.detect(specs_type) do |name_tuple|
+                      name === name_tuple.name
+                    end
+                  end
 
-      output_query_results spec_tuples
-    end
+    output_query_results(spec_tuples)
+  end
 
-    if remote?
-      display_header 'REMOTE'
-
-      fetcher = Gem::SpecFetcher.fetcher
-
-      type = if options[:all]
-               if options[:prerelease]
-                 :complete
-               else
-                 :released
-               end
-             elsif options[:prerelease]
-               :prerelease
-             else
-               :latest
-             end
-
-      if name.respond_to?(:source) && name.source.empty?
-        spec_tuples = fetcher.detect(type) { true }
+  def specs_type
+    if options[:all]
+      if options[:prerelease]
+        :complete
       else
-        spec_tuples = fetcher.detect(type) do |name_tuple|
-          name === name_tuple.name
-        end
+        :released
       end
-
-      output_query_results spec_tuples
+    elsif options[:prerelease]
+      :prerelease
+    else
+      :latest
     end
   end
 
@@ -235,7 +248,7 @@ is too hard to use.
 
     name_tuple, spec = detail_tuple
 
-    spec = spec.fetch_spec name_tuple if spec.respond_to? :fetch_spec
+    spec = spec.fetch_spec(name_tuple)if spec.respond_to?(:fetch_spec)
 
     entry << "\n"
 
@@ -285,8 +298,8 @@ is too hard to use.
 
     entry = [name_tuples.first.name]
 
-    entry_versions entry, name_tuples, platforms, specs
-    entry_details  entry, detail_tuple, specs, platforms
+    entry_versions(entry, name_tuples, platforms, specs)
+    entry_details(entry, detail_tuple, specs, platforms)
 
     entry.join
   end
@@ -337,12 +350,13 @@ is too hard to use.
 
     if platforms.length == 1
       title = platforms.values.length == 1 ? 'Platform' : 'Platforms'
-      entry << "    #{title}: #{platforms.values.sort.join ', '}\n"
+      entry << "    #{title}: #{platforms.values.sort.join(', ')}\n"
     else
       entry << "    Platforms:\n"
-      platforms.sort_by do |version,|
-        version
-      end.each do |version, pls|
+
+      sorted_platforms = platforms.sort_by { |version,| version }
+
+      sorted_platforms.each do |version, pls|
         label = "        #{version}: "
         data = format_text pls.sort.join(', '), 68, label.length
         data[0, label.length] = label
diff --git a/lib/rubygems/commands/setup_command.rb b/lib/rubygems/commands/setup_command.rb
index f5e5236a06..1754630c8c 100644
--- a/lib/rubygems/commands/setup_command.rb
+++ b/lib/rubygems/commands/setup_command.rb
@@ -429,7 +429,7 @@ By default, this RubyGems will install gem as:
     Dir.chdir("bundler") do
       built_gem = Gem::Package.build(bundler_spec)
       begin
-        installer = Gem::Installer.at(built_gem, env_shebang: options[:env_shebang], install_as_default: true, bin_dir: bin_dir, wrappers: true)
+        installer = Gem::Installer.at(built_gem, env_shebang: options[:env_shebang], format_executable: options[:format_executable], install_as_default: true, bin_dir: bin_dir, wrappers: true)
         installer.install
       ensure
         FileUtils.rm_f built_gem
diff --git a/lib/rubygems/commands/update_command.rb b/lib/rubygems/commands/update_command.rb
index 4b182396f3..e8031a259d 100644
--- a/lib/rubygems/commands/update_command.rb
+++ b/lib/rubygems/commands/update_command.rb
@@ -254,9 +254,7 @@ command to remove old versions.
   def update_rubygems_arguments # :nodoc:
     args = []
     args << '--prefix' << Gem.prefix if Gem.prefix
-    # TODO use --document for >= 1.9 , --no-rdoc --no-ri < 1.9
-    args << '--no-rdoc' unless options[:document].include? 'rdoc'
-    args << '--no-ri'   unless options[:document].include? 'ri'
+    args << '--no-document' unless options[:document].include?('rdoc') || options[:document].include?('ri')
     args << '--no-format-executable' if options[:no_format_executable]
     args << '--previous-version' << Gem::VERSION if
       options[:system] == true or
diff --git a/lib/rubygems/core_ext/kernel_gem.rb b/lib/rubygems/core_ext/kernel_gem.rb
index 39b00387ea..fb3053fd83 100644
--- a/lib/rubygems/core_ext/kernel_gem.rb
+++ b/lib/rubygems/core_ext/kernel_gem.rb
@@ -7,9 +7,6 @@
 
 module Kernel
 
-  # REFACTOR: This should be pulled out into some kind of hacks file.
-  remove_method :gem if 'method' == defined? gem # from gem_prelude.rb on 1.9
-
   ##
   # Use Kernel#gem to activate a specific version of +gem_name+.
   #
diff --git a/lib/rubygems/defaults.rb b/lib/rubygems/defaults.rb
index 7aa0480b80..33b6ab3f3e 100644
--- a/lib/rubygems/defaults.rb
+++ b/lib/rubygems/defaults.rb
@@ -148,13 +148,6 @@ module Gem
   end
 
   ##
-  # Whether to expect full paths in default gems - true for non-MRI
-  # ruby implementations
-  def self.default_gems_use_full_paths?
-    ruby_engine != 'ruby'
-  end
-
-  ##
   # Install extensions into lib as well as into the extension directory.
 
   def self.install_extension_in_lib # :nodoc:
diff --git a/lib/rubygems/ext/rake_builder.rb b/lib/rubygems/ext/rake_builder.rb
index 52041a2713..077f080c07 100644
--- a/lib/rubygems/ext/rake_builder.rb
+++ b/lib/rubygems/ext/rake_builder.rb
@@ -20,7 +20,7 @@ class Gem::Ext::RakeBuilder < Gem::Ext::Builder
       rake = rake.shellsplit
     else
       begin
-        rake = [Gem.ruby, "-rrubygems", Gem.bin_path('rake', 'rake')]
+        rake = [Gem.ruby, "-I#{File.expand_path("..", __dir__)}", "-rrubygems", Gem.bin_path('rake', 'rake')]
       rescue Gem::Exception
         rake = [Gem.default_exec_format % 'rake']
       end
diff --git a/lib/rubygems/installer_test_case.rb b/lib/rubygems/installer_test_case.rb
index 1c16959f5f..f48466d3ea 100644
--- a/lib/rubygems/installer_test_case.rb
+++ b/lib/rubygems/installer_test_case.rb
@@ -66,44 +66,9 @@ end
 
 class Gem::InstallerTestCase < Gem::TestCase
 
-  ##
-  # Creates the following instance variables:
-  #
-  # @spec::
-  #   a spec named 'a', intended for regular installs
-  # @user_spec::
-  #   a spec named 'b', intended for user installs
-  #
-  # @gem::
-  #   the path to a built gem from @spec
-  # @user_spec::
-  #   the path to a built gem from @user_spec
-  #
-  # @installer::
-  #   a Gem::Installer for the @spec that installs into @gemhome
-  # @user_installer::
-  #   a Gem::Installer for the @user_spec that installs into Gem.user_dir
-
   def setup
     super
 
-    @spec = quick_gem 'a' do |spec|
-      util_make_exec spec
-    end
-
-    @user_spec = quick_gem 'b' do |spec|
-      util_make_exec spec
-    end
-
-    util_build_gem @spec
-    util_build_gem @user_spec
-
-    @gem = @spec.cache_file
-    @user_gem = @user_spec.cache_file
-
-    @installer      = util_installer @spec, @gemhome
-    @user_installer = util_installer @user_spec, Gem.user_dir, :user
-
     Gem::Installer.path_warning = false
   end
 
@@ -136,6 +101,83 @@ class Gem::InstallerTestCase < Gem::TestCase
   end
 
   ##
+  # Creates the following instance variables:
+  #
+  # @spec::
+  #   a spec named 'a', intended for regular installs
+  #
+  # @gem::
+  #   the path to a built gem from @spec
+  #
+  # And returns a Gem::Installer for the @spec that installs into @gemhome
+
+  def setup_base_installer
+    @gem = setup_base_gem
+    util_installer @spec, @gemhome
+  end
+
+  ##
+  # Creates the following instance variables:
+  #
+  # @spec::
+  #   a spec named 'a', intended for regular installs
+  #
+  # And returns a gem built for the @spec
+
+  def setup_base_gem
+    @spec = setup_base_spec
+    util_build_gem @spec
+    @spec.cache_file
+  end
+
+  ##
+  # Sets up a generic specification for testing the rubygems installer
+  #
+  # And returns it
+
+  def setup_base_spec
+    quick_gem 'a' do |spec|
+      util_make_exec spec
+    end
+  end
+
+  ##
+  # Creates the following instance variables:
+  #
+  # @spec::
+  #   a spec named 'a', intended for regular installs
+  # @user_spec::
+  #   a spec named 'b', intended for user installs
+  #
+  # @gem::
+  #   the path to a built gem from @spec
+  # @user_gem::
+  #   the path to a built gem from @user_spec
+  #
+  # And returns a Gem::Installer for the @user_spec that installs into Gem.user_dir
+
+  def setup_base_user_installer
+    @user_spec = quick_gem 'b' do |spec|
+      util_make_exec spec
+    end
+
+    util_build_gem @user_spec
+
+    @user_gem = @user_spec.cache_file
+
+    util_installer @user_spec, Gem.user_dir, :user
+  end
+
+  ##
+  # Sets up the base @gem, builds it and returns an installer for it.
+  #
+  def util_setup_installer
+    @gem = setup_base_gem
+
+    util_setup_gem
+  end
+
+  ##
   # Builds the @spec gem and returns an installer for it.  The built gem
   # includes:
   #
@@ -143,7 +185,7 @@ class Gem::InstallerTestCase < Gem::TestCase
   #   lib/code.rb
   #   ext/a/mkrf_conf.rb
 
-  def util_setup_gem(ui = @ui) # HACK fix use_ui to make this automatic
+  def util_setup_gem(ui = @ui)
     @spec.files << File.join('lib', 'code.rb')
     @spec.extensions << File.join('ext', 'a', 'mkrf_conf.rb')
 
@@ -175,7 +217,7 @@ class Gem::InstallerTestCase < Gem::TestCase
       end
     end
 
-    @installer = Gem::Installer.at @gem
+    Gem::Installer.at @gem
   end
 
   ##
diff --git a/lib/rubygems/package/tar_header.rb b/lib/rubygems/package/tar_header.rb
index c7b5f88dbd..c37612772a 100644
--- a/lib/rubygems/package/tar_header.rb
+++ b/lib/rubygems/package/tar_header.rb
@@ -107,8 +107,8 @@ class Gem::Package::TarHeader
 
     new :name     => fields.shift,
         :mode     => strict_oct(fields.shift),
-        :uid      => strict_oct(fields.shift),
-        :gid      => strict_oct(fields.shift),
+        :uid      => oct_or_256based(fields.shift),
+        :gid      => oct_or_256based(fields.shift),
         :size     => strict_oct(fields.shift),
         :mtime    => strict_oct(fields.shift),
         :checksum => strict_oct(fields.shift),
@@ -130,6 +130,15 @@ class Gem::Package::TarHeader
     raise ArgumentError, "#{str.inspect} is not an octal string"
   end
 
+  def self.oct_or_256based(str)
+    # \x80 flags a positive 256-based number
+    # \ff flags a negative 256-based number
+    # In case we have a match, parse it as a signed binary value
+    # in big-endian order, except that the high-order bit is ignored.
+    return str.unpack('N2').last if str =~ /\A[\x80\xff]/n
+    strict_oct(str)
+  end
+
   ##
   # Creates a new TarHeader using +vals+
 
diff --git a/lib/rubygems/remote_fetcher.rb b/lib/rubygems/remote_fetcher.rb
index 32c65eada8..a40ee55273 100644
--- a/lib/rubygems/remote_fetcher.rb
+++ b/lib/rubygems/remote_fetcher.rb
@@ -173,7 +173,7 @@ class Gem::RemoteFetcher
         path = source_uri.path
         path = File.dirname(path) if File.extname(path) == '.gem'
 
-        remote_gem_path = correct_for_windows_path(File.join(path, 'gems', gem_file_name))
+        remote_gem_path = Gem::Util.correct_for_windows_path(File.join(path, 'gems', gem_file_name))
 
         FileUtils.cp(remote_gem_path, local_gem_path)
       rescue Errno::EACCES
@@ -210,7 +210,7 @@ class Gem::RemoteFetcher
   # File Fetcher. Dispatched by +fetch_path+. Use it instead.
 
   def fetch_file(uri, *_)
-    Gem.read_binary correct_for_windows_path uri.path
+    Gem.read_binary Gem::Util.correct_for_windows_path uri.path
   end
 
   ##
@@ -317,14 +317,6 @@ class Gem::RemoteFetcher
     response['content-length'].to_i
   end
 
-  def correct_for_windows_path(path)
-    if path[0].chr == '/' && path[1].chr =~ /[a-z]/i && path[2].chr == ':'
-      path[1..-1]
-    else
-      path
-    end
-  end
-
   ##
   # Performs a Net::HTTP request of type +request_class+ on +uri+ returning
   # a Net::HTTP response object.  request maintains a table of persistent
diff --git a/lib/rubygems/request/connection_pools.rb b/lib/rubygems/request/connection_pools.rb
index 7c273d5465..9444239b2c 100644
--- a/lib/rubygems/request/connection_pools.rb
+++ b/lib/rubygems/request/connection_pools.rb
@@ -76,9 +76,7 @@ class Gem::Request::ConnectionPools # :nodoc:
   end
 
   def net_http_args(uri, proxy_uri)
-    # URI::Generic#hostname was added in ruby 1.9.3, use it if exists, otherwise
-    # don't support IPv6 literals and use host.
-    hostname = uri.respond_to?(:hostname) ? uri.hostname : uri.host
+    hostname = uri.hostname
     net_http_args = [hostname, uri.port]
 
     no_proxy = get_no_proxy_from_env
diff --git a/lib/rubygems/resolver.rb b/lib/rubygems/resolver.rb
index d308f68f21..f74995713b 100644
--- a/lib/rubygems/resolver.rb
+++ b/lib/rubygems/resolver.rb
@@ -246,7 +246,7 @@ class Gem::Resolver
     sources.each do |source|
       groups[source].
         sort_by { |spec| [spec.version, Gem::Platform.local =~ spec.platform ? 1 : 0] }.
-        map { |spec| ActivationRequest.new spec, dependency, [] }.
+        map { |spec| ActivationRequest.new spec, dependency }.
         each { |activation_request| activation_requests << activation_request }
     end
 
diff --git a/lib/rubygems/resolver/activation_request.rb b/lib/rubygems/resolver/activation_request.rb
index 7fbabbff50..2a8d6032f8 100644
--- a/lib/rubygems/resolver/activation_request.rb
+++ b/lib/rubygems/resolver/activation_request.rb
@@ -18,14 +18,10 @@ class Gem::Resolver::ActivationRequest
   ##
   # Creates a new ActivationRequest that will activate +spec+.  The parent
   # +request+ is used to provide diagnostics in case of conflicts.
-  #
-  # +others_possible+ indicates that other specifications may also match this
-  # activation request.
 
-  def initialize(spec, request, others_possible = true)
+  def initialize(spec, request)
     @spec = spec
     @request = request
-    @others_possible = others_possible
   end
 
   def ==(other) # :nodoc:
@@ -90,21 +86,8 @@ class Gem::Resolver::ActivationRequest
   end
 
   def inspect # :nodoc:
-    others =
-      case @others_possible
-      when true then # TODO remove at RubyGems 3
-        ' (others possible)'
-      when false then # TODO remove at RubyGems 3
-        nil
-      else
-        unless @others_possible.empty?
-          others = @others_possible.map { |s| s.full_name }
-          " (others possible: #{others.join ', '})"
-        end
-      end
-
-    '#<%s for %p from %s%s>' % [
-      self.class, @spec, @request, others
+    '#<%s for %p from %s>' % [
+      self.class, @spec, @request
     ]
   end
 
@@ -132,19 +115,6 @@ class Gem::Resolver::ActivationRequest
   end
 
   ##
-  # Indicate if this activation is one of a set of possible
-  # requests for the same Dependency request.
-
-  def others_possible?
-    case @others_possible
-    when true, false then
-      @others_possible
-    else
-      not @others_possible.empty?
-    end
-  end
-
-  ##
   # Return the ActivationRequest that contained the dependency
   # that we were activated for.
 
@@ -160,19 +130,6 @@ class Gem::Resolver::ActivationRequest
       q.breakable
       q.text ' for '
       q.pp @request
-
-      case @others_possible
-      when false then
-      when true then
-        q.breakable
-        q.text 'others possible'
-      else
-        unless @others_possible.empty?
-          q.breakable
-          q.text 'others '
-          q.pp @others_possible.map { |s| s.full_name }
-        end
-      end
     end
   end
 
diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index 942e49bf84..c1286369be 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -743,9 +743,6 @@ class Gem::Specification < Gem::BasicSpecification
   def self._all # :nodoc:
     unless defined?(@@all) && @@all
       @@all = stubs.map(&:to_spec)
-      if @@all.any?(&:nil?) # TODO: remove once we're happy
-        raise "pid: #{$$} nil spec! included in #{stubs.inspect}"
-      end
 
       # After a reset, make sure already loaded specs
       # are still marked as activated.
@@ -896,7 +893,6 @@ class Gem::Specification < Gem::BasicSpecification
   # -- wilsonb
 
   def self.all=(specs)
-    raise "nil spec!" if specs.any?(&:nil?) # TODO: remove once we're happy
     @@stubs_by_name = specs.group_by(&:name)
     @@all = @@stubs = specs
   end
@@ -1498,16 +1494,7 @@ class Gem::Specification < Gem::BasicSpecification
 
     paths = full_require_paths
 
-    # gem directories must come after -I and ENV['RUBYLIB']
-    insert_index = Gem.load_path_insert_index
-
-    if insert_index
-      # gem directories must come after -I and ENV['RUBYLIB']
-      $LOAD_PATH.insert(insert_index, *paths)
-    else
-      # we are probably testing in core, -I and RUBYLIB don't apply
-      $LOAD_PATH.unshift(*paths)
-    end
+    Gem.add_to_load_path(*paths)
   end
 
   ##
@@ -1927,8 +1914,7 @@ class Gem::Specification < Gem::BasicSpecification
   end
 
   def gems_dir
-    # TODO: this logic seems terribly broken, but tests fail if just base_dir
-    @gems_dir ||= File.join(loaded_from && base_dir || Gem.dir, "gems")
+    @gems_dir ||= File.join(base_dir, "gems")
   end
 
   ##
diff --git a/lib/rubygems/test_case.rb b/lib/rubygems/test_case.rb
index 8e909e4afe..b466e7a4e0 100644
--- a/lib/rubygems/test_case.rb
+++ b/lib/rubygems/test_case.rb
@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-# TODO: $SAFE = 1
 
 require 'rubygems'
 
@@ -27,13 +26,6 @@ begin
 rescue LoadError
 end
 
-# We have to load these up front because otherwise we'll try to load
-# them while we're testing rubygems, and thus we can't actually load them.
-unless Gem::Dependency.new('rdoc', '>= 3.10').matching_specs.empty?
-  gem 'rdoc'
-  gem 'json'
-end
-
 require 'bundler'
 
 require 'minitest/autorun'
@@ -91,8 +83,6 @@ end
 # gem-related behavior in a sandbox.  Through RubyGemTestCase you can install
 # and uninstall gems, fetch remote gems through a stub fetcher and be assured
 # your normal set of gems is not affected.
-#
-# Tests are always run at a safe level of 1.
 
 class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Unit::TestCase)
 
@@ -152,6 +142,28 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
     end
   end
 
+  ##
+  # Sets the vendordir entry in RbConfig::CONFIG to +value+ and restores the
+  # original value when the block ends
+  #
+  def vendordir(value)
+    vendordir = RbConfig::CONFIG['vendordir']
+
+    if value
+      RbConfig::CONFIG['vendordir'] = value
+    else
+      RbConfig::CONFIG.delete 'vendordir'
+    end
+
+    yield
+  ensure
+    if vendordir
+      RbConfig::CONFIG['vendordir'] = vendordir
+    else
+      RbConfig::CONFIG.delete 'vendordir'
+    end
+  end
+
   # TODO: move to minitest
   def refute_path_exists(path, msg = nil)
     msg = message(msg) { "Expected path '#{path}' to not exist" }
@@ -222,8 +234,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
 
   @@project_dir = Dir.pwd.untaint unless defined?(@@project_dir)
 
-  @@initial_reset = false
-
   ##
   # #setup prepares a sandboxed location to install gems.  All installs are
   # directed to a temporary directory.  All install plugins are removed.
@@ -231,24 +241,11 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
   # If the +RUBY+ environment variable is set the given path is used for
   # Gem::ruby.  The local platform is set to <tt>i386-mswin32</tt> for Windows
   # or <tt>i686-darwin8.10.1</tt> otherwise.
-  #
-  # If the +KEEP_FILES+ environment variable is set the files will not be
-  # removed from <tt>/tmp/test_rubygems_#{$$}.#{Time.now.to_i}</tt>.
 
   def setup
     super
 
-    @orig_gem_home   = ENV['GEM_HOME']
-    @orig_gem_path   = ENV['GEM_PATH']
-    @orig_gem_vendor = ENV['GEM_VENDOR']
-    @orig_gem_spec_cache = ENV['GEM_SPEC_CACHE']
-    @orig_rubygems_gemdeps = ENV['RUBYGEMS_GEMDEPS']
-    @orig_bundle_gemfile   = ENV['BUNDLE_GEMFILE']
-    @orig_rubygems_host = ENV['RUBYGEMS_HOST']
-    ENV.keys.find_all { |k| k.start_with?('GEM_REQUIREMENT_') }.each do |k|
-      ENV.delete k
-    end
-    @orig_gem_env_requirements = ENV.to_hash
+    @orig_env = ENV.to_hash
 
     ENV['GEM_VENDOR'] = nil
     ENV['SOURCE_DATE_EPOCH'] = nil
@@ -256,36 +253,20 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
     @current_dir = Dir.pwd
     @fetcher     = nil
 
-    Bundler.ui = Bundler::UI::Silent.new
-
     @back_ui                       = Gem::DefaultUserInteraction.ui
     @ui                            = Gem::MockGemUi.new
     # This needs to be a new instance since we call use_ui(@ui) when we want to
     # capture output
     Gem::DefaultUserInteraction.ui = Gem::MockGemUi.new
 
-    tmpdir = File.expand_path Dir.tmpdir
+    tmpdir = File.realpath Dir.tmpdir
     tmpdir.untaint
 
-    if ENV['KEEP_FILES']
-      @tempdir = File.join(tmpdir, "test_rubygems_#{$$}.#{Time.now.to_i}")
-    else
-      @tempdir = File.join(tmpdir, "test_rubygems_#{$$}")
-    end
+    @tempdir = File.join(tmpdir, "test_rubygems_#{$$}")
     @tempdir.untaint
 
     FileUtils.mkdir_p @tempdir
 
-    # This makes the tempdir consistent on OS X.
-    # File.expand_path Dir.tmpdir                      #=> "/var/..."
-    # Dir.chdir Dir.tmpdir do File.expand_path '.' end #=> "/private/var/..."
-    # TODO use File#realpath above instead of #expand_path once 1.8 support is
-    # dropped.
-    Dir.chdir @tempdir do
-      @tempdir = File.expand_path '.'
-      @tempdir.untaint
-    end
-
     # This makes the tempdir consistent on Windows.
     # Dir.tmpdir may return short path name, but Dir[Dir.tmpdir] returns long
     # path name. https://bugs.ruby-lang.org/issues/10819
@@ -343,25 +324,21 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
 
     @default_dir = File.join @tempdir, 'default'
     @default_spec_dir = File.join @default_dir, "specifications", "default"
-    Gem.instance_variable_set :@default_dir, @default_dir
-    FileUtils.mkdir_p @default_spec_dir
-
-    # We use Gem::Specification.reset the first time only so that if there
-    # are unresolved deps that leak into the whole test suite, they're at least
-    # reported once.
-    if @@initial_reset
-      Gem::Specification.unresolved_deps.clear # done to avoid cross-test warnings
+    if Gem.java_platform?
+      @orig_default_gem_home = RbConfig::CONFIG['default_gem_home']
+      RbConfig::CONFIG['default_gem_home'] = @default_dir
     else
-      @@initial_reset = true
-      Gem::Specification.reset
+      Gem.instance_variable_set(:@default_dir, @default_dir)
     end
+    FileUtils.mkdir_p @default_spec_dir
+
+    Gem::Specification.unresolved_deps.clear
     Gem.use_paths(@gemhome)
 
     Gem::Security.reset
 
     Gem.loaded_specs.clear
     Gem.clear_default_specs
-    Gem::Specification.unresolved_deps.clear
     Bundler.reset!
 
     Gem.configuration.verbose = true
@@ -395,7 +372,7 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
 
   ##
   # #teardown restores the process to its original state and removes the
-  # tempdir unless the +KEEP_FILES+ environment variable was set.
+  # tempdir
 
   def teardown
     $LOAD_PATH.replace @orig_LOAD_PATH if @orig_LOAD_PATH
@@ -420,33 +397,18 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
 
     Dir.chdir @current_dir
 
-    FileUtils.rm_rf @tempdir unless ENV['KEEP_FILES']
+    FileUtils.rm_rf @tempdir
 
-    ENV.clear
-    @orig_gem_env_requirements.each do |k,v|
-      ENV[k] = v
-    end
-
-    ENV['GEM_HOME']   = @orig_gem_home
-    ENV['GEM_PATH']   = @orig_gem_path
-    ENV['GEM_VENDOR'] = @orig_gem_vendor
-    ENV['GEM_SPEC_CACHE'] = @orig_gem_spec_cache
-    ENV['RUBYGEMS_GEMDEPS'] = @orig_rubygems_gemdeps
-    ENV['BUNDLE_GEMFILE']   = @orig_bundle_gemfile
-    ENV['RUBYGEMS_HOST'] = @orig_rubygems_host
+    ENV.replace(@orig_env)
 
     Gem.ruby = @orig_ruby if @orig_ruby
 
-    if @orig_ENV_HOME
-      ENV['HOME'] = @orig_ENV_HOME
+    if Gem.java_platform?
+      RbConfig::CONFIG['default_gem_home'] = @orig_default_gem_home
     else
-      ENV.delete 'HOME'
+      Gem.instance_variable_set :@default_dir, nil
     end
 
-    Gem.instance_variable_set :@default_dir, nil
-
-    ENV['GEM_PRIVATE_KEY_PASSPHRASE'] = @orig_gem_private_key_passphrase
-
     Gem::Specification._clear_load_cache
     Gem::Specification.unresolved_deps.clear
     Gem::refresh
@@ -594,22 +556,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
   end
 
   ##
-  # creates a temporary directory with hax
-  # TODO: deprecate and remove
-
-  def create_tmpdir
-    tmpdir = nil
-
-    Dir.chdir Dir.tmpdir do
-      tmpdir = Dir.pwd
-    end # HACK OSX /private/tmp
-
-    tmpdir = File.join tmpdir, "test_rubygems_#{$$}"
-    FileUtils.mkdir_p tmpdir
-    return tmpdir
-  end
-
-  ##
   # Enables pretty-print for all tests
 
   def mu_pp(obj)
@@ -686,7 +632,7 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
       io.write spec.to_ruby_for_cache
     end
 
-    spec.loaded_from = spec.loaded_from = written_path
+    spec.loaded_from = written_path
 
     Gem::Specification.reset
 
@@ -694,14 +640,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
   end
 
   ##
-  # TODO:  remove in RubyGems 4.0
-
-  def quick_spec(name, version = '2') # :nodoc:
-    util_spec name, version
-  end
-  deprecate :quick_spec, :util_spec, 2018, 12
-
-  ##
   # Builds a gem from +spec+ and places it in <tt>File.join @gemhome,
   # 'cache'</tt>.  Automatically creates files based on +spec.files+
 
@@ -744,11 +682,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
     Gem::Specification.reset
   end
 
-  def util_clear_default_gems
-    FileUtils.rm_rf @default_spec_dir
-    FileUtils.mkdir @default_spec_dir
-  end
-
   ##
   # Install the provided specs
 
@@ -802,52 +735,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
     $LOADED_FEATURES.replace old_loaded_features
   end
 
-  ##
-  # new_spec is deprecated as it is never used.
-  #
-  # TODO:  remove in RubyGems 4.0
-
-  def new_spec(name, version, deps = nil, *files) # :nodoc:
-    require 'rubygems/specification'
-
-    spec = Gem::Specification.new do |s|
-      s.platform    = Gem::Platform::RUBY
-      s.name        = name
-      s.version     = version
-      s.author      = 'A User'
-      s.email       = 'example@example.com'
-      s.homepage    = 'http://example.com'
-      s.summary     = "this is a summary"
-      s.description = "This is a test description"
-
-      Array(deps).each do |n, req|
-        s.add_dependency n, (req || '>= 0')
-      end
-
-      s.files.push(*files) unless files.empty?
-
-      yield s if block_given?
-    end
-
-    spec.loaded_from = spec.spec_file
-
-    unless files.empty?
-      write_file spec.spec_file do |io|
-        io.write spec.to_ruby_for_cache
-      end
-
-      util_build_gem spec
-
-      cache_file = File.join @tempdir, 'gems', "#{spec.full_name}.gem"
-      FileUtils.mkdir_p File.dirname cache_file
-      FileUtils.mv spec.cache_file, cache_file
-      FileUtils.rm spec.spec_file
-    end
-
-    spec
-  end
-  deprecate :new_spec, :none, 2018, 12
-
   def new_default_spec(name, version, deps = nil, *files)
     spec = util_spec name, version, deps
 
@@ -910,8 +797,6 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
       FileUtils.rm spec.spec_file
     end
 
-    Gem::Specification.reset
-
     return spec
   end
 
@@ -1061,31 +946,6 @@ Also, a list:
   end
 
   ##
-  # Sets up a fake fetcher using the gems from #util_make_gems.  Optionally
-  # additional +prerelease+ gems may be included.
-  #
-  # Gems created by this method may be fetched using Gem::RemoteFetcher.
-
-  def util_setup_fake_fetcher(prerelease = false)
-    require 'zlib'
-    require 'socket'
-    require 'rubygems/remote_fetcher'
-
-    @fetcher = Gem::FakeFetcher.new
-
-    util_make_gems(prerelease)
-    Gem::Specification.reset
-
-    @all_gems = [@a1, @a2, @a3a, @a_evil9, @b2, @c1_2].sort
-    @all_gem_names = @all_gems.map { |gem| gem.full_name }
-
-    gem_names = [@a1.full_name, @a2.full_name, @a3a.full_name, @b2.full_name]
-    @gem_names = gem_names.sort.join("\n")
-
-    Gem::RemoteFetcher.fetcher = @fetcher
-  end
-
-  ##
   # Add +spec+ to +@fetcher+ serving the data in the file +path+.
   # +repo+ indicates which repo to make +spec+ appear to be in.
 
@@ -1096,7 +956,6 @@ Also, a list:
 
   ##
   # Sets up Gem::SpecFetcher to return information from the gems in +specs+.
-  # Best used with +@all_gems+ from #util_setup_fake_fetcher.
 
   def util_setup_spec_fetcher(*specs)
     all_specs = Gem::Specification.to_a + specs
@@ -1163,8 +1022,7 @@ Also, a list:
   end
 
   def util_set_RUBY_VERSION(version, patchlevel = nil, revision = nil, description = nil, engine = "ruby", engine_version = nil)
-    if Gem.instance_variables.include? :@ruby_version or
-       Gem.instance_variables.include? '@ruby_version'
+    if Gem.instance_variables.include? :@ruby_version
       Gem.send :remove_instance_variable, :@ruby_version
     end
 
@@ -1224,6 +1082,20 @@ Also, a list:
   end
 
   ##
+  # Is this test being run on a Java platform?
+
+  def self.java_platform?
+    Gem.java_platform?
+  end
+
+  ##
+  # Is this test being run on a Java platform?
+
+  def java_platform?
+    Gem.java_platform?
+  end
+
+  ##
   # Returns whether or not we're on a version of Ruby built with VC++ (or
   # Borland) versus Cygwin, Mingw, etc.
 
@@ -1623,10 +1495,3 @@ rescue LoadError, Gem::LoadError
 end
 
 require 'rubygems/test_utilities'
-tmpdirs = []
-tmpdirs << (ENV['GEM_HOME'] = Dir.mktmpdir("home"))
-tmpdirs << (ENV['GEM_PATH'] = Dir.mktmpdir("path"))
-pid = $$
-END {tmpdirs.each {|dir| Dir.rmdir(dir)} if $$ == pid}
-Gem.clear_paths
-Gem.loaded_specs.clear
diff --git a/lib/rubygems/test_utilities.rb b/lib/rubygems/test_utilities.rb
index 5d02b04897..69ff05370e 100644
--- a/lib/rubygems/test_utilities.rb
+++ b/lib/rubygems/test_utilities.rb
@@ -241,21 +241,22 @@ class Gem::TestCase::SpecFetcherSetup
 
   def execute_operations # :nodoc:
     @operations.each do |operation, *arguments|
+      block = arguments.pop
       case operation
       when :gem then
-        spec, gem = @test.util_gem(*arguments, &arguments.pop)
+        spec, gem = @test.util_gem(*arguments, &block)
 
         write_spec spec
 
         @gems[spec] = gem
         @installed << spec
       when :download then
-        spec, gem = @test.util_gem(*arguments, &arguments.pop)
+        spec, gem = @test.util_gem(*arguments, &block)
 
         @gems[spec] = gem
         @downloaded << spec
       when :spec then
-        spec = @test.util_spec(*arguments, &arguments.pop)
+        spec = @test.util_spec(*arguments, &block)
 
         write_spec spec
 
diff --git a/lib/rubygems/util.rb b/lib/rubygems/util.rb
index 401e5609f7..b5f1408401 100644
--- a/lib/rubygems/util.rb
+++ b/lib/rubygems/util.rb
@@ -44,29 +44,10 @@ module Gem::Util
   end
 
   ##
-  # This calls IO.popen where it accepts an array for a +command+ (Ruby 1.9+)
-  # and implements an IO.popen-like behavior where it does not accept an array
-  # for a command.
+  # This calls IO.popen and reads the result
 
   def self.popen(*command)
     IO.popen command, &:read
-  rescue TypeError # ruby 1.8 only supports string command
-    r, w = IO.pipe
-
-    pid = fork do
-      STDIN.close
-      STDOUT.reopen w
-
-      exec(*command)
-    end
-
-    w.close
-
-    begin
-      return r.read
-    ensure
-      Process.wait pid
-    end
   end
 
   ##
@@ -80,26 +61,7 @@ module Gem::Util
     else
       cmds = command.dup
     end
-    return system(*(cmds << opt))
-  rescue TypeError
-    @silent_mutex ||= Mutex.new
-
-    @silent_mutex.synchronize do
-      begin
-        stdout = STDOUT.dup
-        stderr = STDERR.dup
-
-        STDOUT.reopen IO::NULL, 'w'
-        STDERR.reopen IO::NULL, 'w'
-
-        return system(*command)
-      ensure
-        STDOUT.reopen stdout
-        STDERR.reopen stderr
-        stdout.close
-        stderr.close
-      end
-    end
+    system(*(cmds << opt))
   end
 
   ##
@@ -130,4 +92,16 @@ module Gem::Util
     end
   end
 
+  ##
+  # Corrects +path+ (usually returned by `URI.parse().path` on Windows), that
+  # comes with a leading slash.
+
+  def self.correct_for_windows_path(path)
+    if path[0].chr == '/' && path[1].chr =~ /[a-z]/i && path[2].chr == ':'
+      path[1..-1]
+    else
+      path
+    end
+  end
+
 end
diff --git a/test/rubygems/test_gem.rb b/test/rubygems/test_gem.rb
index af927ffa29..c90ad2d41a 100644
--- a/test/rubygems/test_gem.rb
+++ b/test/rubygems/test_gem.rb
@@ -465,55 +465,43 @@ class TestGem < Gem::TestCase
   end
 
   def test_default_path
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG['vendordir'] = File.join @tempdir, 'vendor'
+    vendordir(File.join(@tempdir, 'vendor')) do
+      FileUtils.rm_rf Gem.user_home
 
-    FileUtils.rm_rf Gem.user_home
+      expected = [Gem.default_dir]
 
-    expected = [Gem.default_dir]
-
-    assert_equal expected, Gem.default_path
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      assert_equal expected, Gem.default_path
+    end
   end
 
   def test_default_path_missing_vendor
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG.delete 'vendordir'
-
-    FileUtils.rm_rf Gem.user_home
+    vendordir(nil) do
+      FileUtils.rm_rf Gem.user_home
 
-    expected = [Gem.default_dir]
+      expected = [Gem.default_dir]
 
-    assert_equal expected, Gem.default_path
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      assert_equal expected, Gem.default_path
+    end
   end
 
   def test_default_path_user_home
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG['vendordir'] = File.join @tempdir, 'vendor'
+    vendordir(File.join(@tempdir, 'vendor')) do
+      expected = [Gem.user_dir, Gem.default_dir]
 
-    expected = [Gem.user_dir, Gem.default_dir]
-
-    assert_equal expected, Gem.default_path
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      assert_equal expected, Gem.default_path
+    end
   end
 
   def test_default_path_vendor_dir
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG['vendordir'] = File.join @tempdir, 'vendor'
-
-    FileUtils.mkdir_p Gem.vendor_dir
+    vendordir(File.join(@tempdir, 'vendor')) do
+      FileUtils.mkdir_p Gem.vendor_dir
 
-    FileUtils.rm_rf Gem.user_home
+      FileUtils.rm_rf Gem.user_home
 
-    expected = [Gem.default_dir, Gem.vendor_dir]
+      expected = [Gem.default_dir, Gem.vendor_dir]
 
-    assert_equal expected, Gem.default_path
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      assert_equal expected, Gem.default_path
+    end
   end
 
   def test_self_default_sources
@@ -706,7 +694,7 @@ class TestGem < Gem::TestCase
     assert_equal expected, Gem.find_files('sff/discover').sort
     assert_equal expected, Gem.find_files('sff/**.rb').sort, '[ruby-core:31730]'
   ensure
-    assert_equal cwd, actual_load_path.shift
+    assert_equal cwd, actual_load_path.shift unless Gem.java_platform?
   end
 
   def test_self_find_latest_files
@@ -1232,10 +1220,12 @@ class TestGem < Gem::TestCase
       refute Gem.try_activate 'nonexistent'
     end
 
-    expected = "Ignoring ext-1 because its extensions are not built. " +
-               "Try: gem pristine ext --version 1\n"
+    unless Gem.java_platform?
+      expected = "Ignoring ext-1 because its extensions are not built. " +
+                 "Try: gem pristine ext --version 1\n"
 
-    assert_equal expected, err
+      assert_equal expected, err
+    end
   end
 
   def test_self_use_paths_with_nils
@@ -1303,7 +1293,6 @@ class TestGem < Gem::TestCase
   end
 
   def test_self_needs
-    util_clear_gems
     a = util_spec "a", "1"
     b = util_spec "b", "1", "c" => nil
     c = util_spec "c", "2"
@@ -1322,7 +1311,6 @@ class TestGem < Gem::TestCase
 
   def test_self_needs_picks_up_unresolved_deps
     save_loaded_features do
-      util_clear_gems
       a = util_spec "a", "1"
       b = util_spec "b", "1", "c" => nil
       c = util_spec "c", "2"
@@ -1364,11 +1352,13 @@ class TestGem < Gem::TestCase
   end
 
   def test_self_vendor_dir
-    expected =
-      File.join RbConfig::CONFIG['vendordir'], 'gems',
-                RbConfig::CONFIG['ruby_version']
+    vendordir(File.join(@tempdir, 'vendor')) do
+      expected =
+        File.join RbConfig::CONFIG['vendordir'], 'gems',
+                  RbConfig::CONFIG['ruby_version']
 
-    assert_equal expected, Gem.vendor_dir
+      assert_equal expected, Gem.vendor_dir
+    end
   end
 
   def test_self_vendor_dir_ENV_GEM_VENDOR
@@ -1379,12 +1369,9 @@ class TestGem < Gem::TestCase
   end
 
   def test_self_vendor_dir_missing
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG.delete 'vendordir'
-
-    assert_nil Gem.vendor_dir
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+    vendordir(nil) do
+      assert_nil Gem.vendor_dir
+    end
   end
 
   def test_load_plugins
@@ -1514,8 +1501,6 @@ class TestGem < Gem::TestCase
   end
 
   def test_auto_activation_of_specific_gemdeps_file
-    util_clear_gems
-
     a = util_spec "a", "1", nil, "lib/a.rb"
     b = util_spec "b", "1", nil, "lib/b.rb"
     c = util_spec "c", "1", nil, "lib/c.rb"
@@ -1538,8 +1523,6 @@ class TestGem < Gem::TestCase
   end
 
   def test_auto_activation_of_used_gemdeps_file
-    util_clear_gems
-
     a = util_spec "a", "1", nil, "lib/a.rb"
     b = util_spec "b", "1", nil, "lib/b.rb"
     c = util_spec "c", "1", nil, "lib/c.rb"
@@ -1571,7 +1554,7 @@ class TestGem < Gem::TestCase
   end
 
   def test_looks_for_gemdeps_files_automatically_on_start
-    util_clear_gems
+    skip "Requiring bundler messes things up" if Gem.java_platform?
 
     a = util_spec "a", "1", nil, "lib/a.rb"
     b = util_spec "b", "1", nil, "lib/b.rb"
@@ -1607,7 +1590,7 @@ class TestGem < Gem::TestCase
   end
 
   def test_looks_for_gemdeps_files_automatically_on_start_in_parent_dir
-    util_clear_gems
+    skip "Requiring bundler messes things up" if Gem.java_platform?
 
     a = util_spec "a", "1", nil, "lib/a.rb"
     b = util_spec "b", "1", nil, "lib/b.rb"
@@ -1674,33 +1657,6 @@ class TestGem < Gem::TestCase
     assert_nil              Gem.find_unresolved_default_spec("README")
   end
 
-  def test_default_gems_use_full_paths
-    begin
-      if defined?(RUBY_ENGINE)
-        engine = RUBY_ENGINE
-        Object.send :remove_const, :RUBY_ENGINE
-      end
-      Object.const_set :RUBY_ENGINE, 'ruby'
-
-      refute Gem.default_gems_use_full_paths?
-    ensure
-      Object.send :remove_const, :RUBY_ENGINE
-      Object.const_set :RUBY_ENGINE, engine if engine
-    end
-
-    begin
-      if defined?(RUBY_ENGINE)
-        engine = RUBY_ENGINE
-        Object.send :remove_const, :RUBY_ENGINE
-      end
-      Object.const_set :RUBY_ENGINE, 'jruby'
-      assert Gem.default_gems_use_full_paths?
-    ensure
-      Object.send :remove_const, :RUBY_ENGINE
-      Object.const_set :RUBY_ENGINE, engine if engine
-    end
-  end
-
   def test_use_gemdeps
     gem_deps_file = 'gem.deps.rb'.untaint
     spec = util_spec 'a', 1
diff --git a/test/rubygems/test_gem_commands_build_command.rb b/test/rubygems/test_gem_commands_build_command.rb
index 6441587cf6..58fc9648bf 100644
--- a/test/rubygems/test_gem_commands_build_command.rb
+++ b/test/rubygems/test_gem_commands_build_command.rb
@@ -281,7 +281,7 @@ class TestGemCommandsBuildCommand < Gem::TestCase
   end
 
   def test_build_signed_gem
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    skip 'openssl is missing' unless defined?(OpenSSL::SSL) && !java_platform?
 
     trust_dir = Gem::Security.trust_dir
 
@@ -308,7 +308,7 @@ class TestGemCommandsBuildCommand < Gem::TestCase
   end
 
   def test_build_signed_gem_with_cert_expiration_length_days
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    skip 'openssl is missing' unless defined?(OpenSSL::SSL) && !java_platform?
 
     gem_path = File.join Gem.user_home, ".gem"
     Dir.mkdir gem_path
@@ -352,7 +352,7 @@ class TestGemCommandsBuildCommand < Gem::TestCase
   end
 
   def test_build_auto_resign_cert
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    skip 'openssl is missing' unless defined?(OpenSSL::SSL) && !java_platform?
 
     gem_path = File.join Gem.user_home, ".gem"
     Dir.mkdir gem_path
@@ -389,7 +389,7 @@ class TestGemCommandsBuildCommand < Gem::TestCase
     output = @ui.output.split "\n"
     assert_equal "INFO:  Your certificate has expired, trying to re-sign it...", output.shift
     assert_equal "INFO:  Your cert: #{tmp_expired_cert_file } has been auto re-signed with the key: #{tmp_private_key_file}", output.shift
-    assert_match /INFO:  Your expired cert will be located at: .+\Wgem-public_cert\.pem\.expired\.[0-9]+/, output.shift
+    assert_match(/INFO:  Your expired cert will be located at: .+\Wgem-public_cert\.pem\.expired\.[0-9]+/, output.shift)
   end
 
 end
diff --git a/test/rubygems/test_gem_commands_cert_command.rb b/test/rubygems/test_gem_commands_cert_command.rb
index d7381f14d0..e9e1a353c1 100644
--- a/test/rubygems/test_gem_commands_cert_command.rb
+++ b/test/rubygems/test_gem_commands_cert_command.rb
@@ -6,6 +6,10 @@ unless defined?(OpenSSL::SSL)
   warn 'Skipping `gem cert` tests.  openssl not found.'
 end
 
+if Gem.java_platform?
+  warn 'Skipping `gem cert` tests on jruby.'
+end
+
 class TestGemCommandsCertCommand < Gem::TestCase
 
   ALTERNATE_CERT = load_cert 'alternate'
@@ -793,4 +797,4 @@ ERROR:  --private-key not specified and ~/.gem/gem-private_key.pem does not exis
                  e.message
   end
 
-end if defined?(OpenSSL::SSL)
+end if defined?(OpenSSL::SSL) && !Gem.java_platform?
diff --git a/test/rubygems/test_gem_commands_query_command.rb b/test/rubygems/test_gem_commands_query_command.rb
index 71cf386026..6183e592e9 100644
--- a/test/rubygems/test_gem_commands_query_command.rb
+++ b/test/rubygems/test_gem_commands_query_command.rb
@@ -459,7 +459,28 @@ pl (1 i386-linux)
     EOF
 
     assert_equal expected, @stub_ui.output
-    assert_equal "WARNING:  prereleases are always shown locally\n", @stub_ui.error
+  end
+
+  def test_execute_no_prerelease_local
+    spec_fetcher do |fetcher|
+      fetcher.legacy_platform
+    end
+
+    @cmd.handle_options %w[-l --no-prerelease]
+
+    use_ui @stub_ui do
+      @cmd.execute
+    end
+
+    expected = <<-EOF
+
+*** LOCAL GEMS ***
+
+a (2, 1)
+pl (1 i386-linux)
+    EOF
+
+    assert_equal expected, @stub_ui.output
   end
 
   def test_execute_remote
@@ -569,7 +590,7 @@ pl (1 i386-linux)
     @cmd.options[:domain] = :remote
 
     use_ui @stub_ui do
-      @cmd.send :show_gems, /a/i, false
+      @cmd.send :show_gems, /a/i
     end
 
     assert_match %r%^a %,  @stub_ui.output
diff --git a/test/rubygems/test_gem_commands_setup_command.rb b/test/rubygems/test_gem_commands_setup_command.rb
index 3f9887eedf..0345386804 100644
--- a/test/rubygems/test_gem_commands_setup_command.rb
+++ b/test/rubygems/test_gem_commands_setup_command.rb
@@ -189,7 +189,7 @@ class TestGemCommandsSetupCommand < Gem::TestCase
         assert_path_exists File.join(bin_dir, "#{e}.bat")
       end
 
-      assert_path_exists File.join bin_dir, e
+      assert_path_exists File.join bin_dir, Gem.default_exec_format % e
     end
 
     default_dir = Gem::Specification.default_specifications_dir
@@ -323,4 +323,4 @@ class TestGemCommandsSetupCommand < Gem::TestCase
     @ui.outs.set_encoding @default_external if @default_external
   end
 
-end
+end unless Gem.java_platform?
diff --git a/test/rubygems/test_gem_commands_sources_command.rb b/test/rubygems/test_gem_commands_sources_command.rb
index 1e58643566..36e6ee9293 100644
--- a/test/rubygems/test_gem_commands_sources_command.rb
+++ b/test/rubygems/test_gem_commands_sources_command.rb
@@ -7,11 +7,17 @@ class TestGemCommandsSourcesCommand < Gem::TestCase
   def setup
     super
 
-    spec_fetcher
-
     @cmd = Gem::Commands::SourcesCommand.new
 
     @new_repo = "http://beta-gems.example.com"
+
+    @old_https_proxy_config = Gem.configuration[:http_proxy]
+  end
+
+  def teardown
+    Gem.configuration[:http_proxy] = @old_https_proxy_config
+
+    super
   end
 
   def test_initialize_proxy
@@ -69,6 +75,8 @@ class TestGemCommandsSourcesCommand < Gem::TestCase
   end
 
   def test_execute_add_nonexistent_source
+    spec_fetcher
+
     uri = "http://beta-gems.example.com/specs.#{@marshal_version}.gz"
     @fetcher.data[uri] = proc do
       raise Gem::RemoteFetcher::FetchError.new('it died', uri)
@@ -92,6 +100,8 @@ Error fetching http://beta-gems.example.com:
   end
 
   def test_execute_add_redundant_source
+    spec_fetcher
+
     @cmd.handle_options %W[--add #{@gem_repo}]
 
     use_ui @ui do
@@ -109,6 +119,8 @@ source #{@gem_repo} already present in the cache
   end
 
   def test_execute_add_redundant_source_trailing_slash
+    spec_fetcher
+
     # Remove pre-existing gem source (w/ slash)
     repo_with_slash = "http://gems.example.com/"
     @cmd.handle_options %W[--remove #{repo_with_slash}]
@@ -266,6 +278,8 @@ beta-gems.example.com is not a URI
   end
 
   def test_execute_remove_no_network
+    spec_fetcher
+
     @cmd.handle_options %W[--remove #{@gem_repo}]
 
     @fetcher.data["#{@gem_repo}Marshal.#{Gem.marshal_version}"] = proc do
diff --git a/test/rubygems/test_gem_commands_uninstall_command.rb b/test/rubygems/test_gem_commands_uninstall_command.rb
index 34b1838486..4ac06977e3 100644
--- a/test/rubygems/test_gem_commands_uninstall_command.rb
+++ b/test/rubygems/test_gem_commands_uninstall_command.rb
@@ -6,19 +6,13 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
 
   def setup
     super
-    common_installer_setup
-
-    build_rake_in do
-      use_ui @ui do
-        @installer.install
-      end
-    end
-
     @cmd = Gem::Commands::UninstallCommand.new
     @executable = File.join(@gemhome, 'bin', 'executable')
   end
 
   def test_execute_all_named
+    initial_install
+
     util_make_gems
 
     default = new_default_spec 'default', '1'
@@ -48,6 +42,8 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_dependency_order
+    initial_install
+
     c = quick_gem 'c' do |spec|
       spec.add_dependency 'a'
     end
@@ -76,15 +72,7 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_removes_executable
-    ui = Gem::MockGemUi.new
-
-    util_setup_gem ui
-
-    build_rake_in do
-      use_ui ui do
-        @installer.install
-      end
-    end
+    initial_install
 
     if win_platform?
       assert File.exist?(@executable)
@@ -113,12 +101,14 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_removes_formatted_executable
+    installer = setup_base_installer
+
     FileUtils.rm_f @executable # Wish this didn't happen in #setup
 
     Gem::Installer.exec_format = 'foo-%s-bar'
 
-    @installer.format_executable = true
-    @installer.install
+    installer.format_executable = true
+    installer.install
 
     formatted_executable = File.join @gemhome, 'bin', 'foo-executable-bar'
     assert_equal true, File.exist?(formatted_executable)
@@ -137,11 +127,11 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
     @gem = File.join @tempdir, @spec.file_name
     FileUtils.touch @gem
 
-    util_setup_gem
+    installer = util_setup_gem
 
     build_rake_in do
       use_ui @ui do
-        @installer.install
+        installer.install
       end
     end
 
@@ -157,10 +147,11 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_with_version_leaves_non_matching_versions
+    initial_install
+
     ui = Gem::MockGemUi.new
 
     util_make_gems
-    util_setup_gem ui
 
     assert_equal 3, Gem::Specification.find_all_by_name('a').length
 
@@ -178,10 +169,11 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_with_version_specified_as_colon
+    initial_install
+
     ui = Gem::MockGemUi.new "y\n"
 
     util_make_gems
-    util_setup_gem ui
 
     assert_equal 3, Gem::Specification.find_all_by_name('a').length
 
@@ -254,6 +246,8 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_with_force_and_without_version_uninstalls_everything
+    initial_install
+
     ui = Gem::MockGemUi.new "y\n"
 
     a_1, = util_gem 'a', 1
@@ -262,8 +256,6 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
     a_3a, = util_gem 'a', '3.a'
     install_gem a_3a
 
-    util_setup_gem ui
-
     assert_equal 3, Gem::Specification.find_all_by_name('a').length
 
     @cmd.options[:force] = true
@@ -279,10 +271,11 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_execute_with_force_ignores_dependencies
+    initial_install
+
     ui = Gem::MockGemUi.new
 
     util_make_gems
-    util_setup_gem ui
 
     assert Gem::Specification.find_all_by_name('dep_x').length > 0
     assert Gem::Specification.find_all_by_name('x').length > 0
@@ -359,20 +352,22 @@ class TestGemCommandsUninstallCommand < Gem::InstallerTestCase
   end
 
   def test_handle_options_vendor
-    use_ui @ui do
-      @cmd.handle_options %w[--vendor]
-    end
+    vendordir(File.join(@tempdir, 'vendor')) do
+      use_ui @ui do
+        @cmd.handle_options %w[--vendor]
+      end
 
-    assert @cmd.options[:vendor]
-    assert_equal Gem.vendor_dir, @cmd.options[:install_dir]
+      assert @cmd.options[:vendor]
+      assert_equal Gem.vendor_dir, @cmd.options[:install_dir]
 
-    assert_empty @ui.output
+      assert_empty @ui.output
 
-    expected = <<-EXPECTED
+      expected = <<-EXPECTED
 WARNING:  Use your OS package manager to uninstall vendor gems
-    EXPECTED
+      EXPECTED
 
-    assert_match expected, @ui.error
+      assert_match expected, @ui.error
+    end
   end
 
   def test_execute_two_version
@@ -395,21 +390,17 @@ WARNING:  Use your OS package manager to uninstall vendor gems
   end
 
   def test_handle_options_vendor_missing
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG.delete 'vendordir'
-
-    e = assert_raises OptionParser::InvalidOption do
-      @cmd.handle_options %w[--vendor]
-    end
-
-    assert_equal 'invalid option: --vendor your platform is not supported',
-                 e.message
+    vendordir(nil) do
+      e = assert_raises OptionParser::InvalidOption do
+        @cmd.handle_options %w[--vendor]
+      end
 
-    refute @cmd.options[:vendor]
-    refute @cmd.options[:install_dir]
+      assert_equal 'invalid option: --vendor your platform is not supported',
+                   e.message
 
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      refute @cmd.options[:vendor]
+      refute @cmd.options[:install_dir]
+    end
   end
 
   def test_execute_with_gem_not_installed
@@ -425,6 +416,8 @@ WARNING:  Use your OS package manager to uninstall vendor gems
   end
 
   def test_execute_with_gem_uninstall_error
+    initial_install
+
     util_make_gems
 
     @cmd.options[:args] = %w[a]
@@ -451,4 +444,17 @@ WARNING:  Use your OS package manager to uninstall vendor gems
     assert_match %r!Error: unable to successfully uninstall '#{@spec.name}'!, @ui.error
   end
 
+  private
+
+  def initial_install
+    installer = setup_base_installer
+    common_installer_setup
+
+    build_rake_in do
+      use_ui @ui do
+        installer.install
+      end
+    end
+  end
+
 end
diff --git a/test/rubygems/test_gem_commands_update_command.rb b/test/rubygems/test_gem_commands_update_command.rb
index 77851d32d6..d9ee5f8468 100644
--- a/test/rubygems/test_gem_commands_update_command.rb
+++ b/test/rubygems/test_gem_commands_update_command.rb
@@ -504,25 +504,12 @@ class TestGemCommandsUpdateCommand < Gem::TestCase
 
     assert_equal '--prefix',           arguments.shift
     assert_equal Gem.prefix,           arguments.shift
-    assert_equal '--no-rdoc',          arguments.shift
-    assert_equal '--no-ri',            arguments.shift
+    assert_equal '--no-document',      arguments.shift
     assert_equal '--previous-version', arguments.shift
     assert_equal Gem::VERSION,         arguments.shift
     assert_empty arguments
   end
 
-  def test_update_rubygems_arguments_1_8_x
-    @cmd.options[:system] = '1.8.26'
-
-    arguments = @cmd.update_rubygems_arguments
-
-    assert_equal '--prefix',           arguments.shift
-    assert_equal Gem.prefix,           arguments.shift
-    assert_equal '--no-rdoc',          arguments.shift
-    assert_equal '--no-ri',            arguments.shift
-    assert_empty arguments
-  end
-
   def test_explain
     spec_fetcher do |fetcher|
       fetcher.download 'a', 2
diff --git a/test/rubygems/test_gem_dependency_installer.rb b/test/rubygems/test_gem_dependency_installer.rb
index 48912ee0cd..15fc8c7c28 100644
--- a/test/rubygems/test_gem_dependency_installer.rb
+++ b/test/rubygems/test_gem_dependency_installer.rb
@@ -45,7 +45,6 @@ class TestGemDependencyInstaller < Gem::TestCase
       s.add_development_dependency 'c'
     end
 
-    util_clear_gems
     util_reset_gems
   end
 
@@ -133,7 +132,6 @@ class TestGemDependencyInstaller < Gem::TestCase
     p1a, gem = util_gem 'a', '10.a'
 
     util_setup_spec_fetcher(p1a, @a1, @a1_pre)
-    util_clear_gems
 
     p1a_data = Gem.read_binary(gem)
 
@@ -172,7 +170,6 @@ class TestGemDependencyInstaller < Gem::TestCase
     p1a, gem = util_gem 'p', '1.a'
 
     util_setup_spec_fetcher(p1a)
-    util_clear_gems
 
     p1a_data = Gem.read_binary(gem)
 
@@ -192,7 +189,6 @@ class TestGemDependencyInstaller < Gem::TestCase
     util_setup_gems
 
     util_setup_spec_fetcher(@a1, @a1_pre)
-    util_clear_gems
 
     p1a_data = Gem.read_binary(@a1_gem)
 
@@ -213,8 +209,6 @@ class TestGemDependencyInstaller < Gem::TestCase
       s.add_dependency 'b'
     end
 
-    util_clear_gems
-
     FileUtils.mv @a1_gem, @tempdir
     FileUtils.mv @b1_gem, @tempdir
     FileUtils.mv  e1_gem, @tempdir
@@ -575,8 +569,6 @@ class TestGemDependencyInstaller < Gem::TestCase
       s.add_dependency 'a'
     end
 
-    util_clear_gems
-
     FileUtils.mv @a1_gem, @tempdir
     FileUtils.mv @b1_gem, @tempdir
     FileUtils.mv  b2_gem, @tempdir
@@ -877,8 +869,6 @@ class TestGemDependencyInstaller < Gem::TestCase
 
     si = util_setup_spec_fetcher @a1, a2_o
 
-    util_clear_gems
-
     @fetcher.data['http://gems.example.com/gems/yaml'] = si.to_yaml
 
     a1_data = nil
@@ -1274,8 +1264,6 @@ class TestGemDependencyInstaller < Gem::TestCase
     util_setup_spec_fetcher(*[@a1, @a1_pre, @b1, @c1_pre,
                               @d1, @d2, @x1_m, @x1_o, @w1, @y1,
                               @y1_1_p, @z1].compact)
-
-    util_clear_gems
   end
 
 end
diff --git a/test/rubygems/test_gem_dependency_list.rb b/test/rubygems/test_gem_dependency_list.rb
index 019cb33973..6bf803fe5f 100644
--- a/test/rubygems/test_gem_dependency_list.rb
+++ b/test/rubygems/test_gem_dependency_list.rb
@@ -7,8 +7,6 @@ class TestGemDependencyList < Gem::TestCase
   def setup
     super
 
-    util_clear_gems
-
     @deplist = Gem::DependencyList.new
 
     # TODO: switch to util_spec
@@ -124,8 +122,6 @@ class TestGemDependencyList < Gem::TestCase
   end
 
   def test_ok_eh
-    util_clear_gems
-
     assert @deplist.ok?, 'no dependencies'
 
     @deplist.add @b2
@@ -138,8 +134,6 @@ class TestGemDependencyList < Gem::TestCase
   end
 
   def test_why_not_ok_eh
-    util_clear_gems
-
     assert_equal({},  @deplist.why_not_ok?)
 
     @deplist.add @b2
@@ -229,8 +223,6 @@ class TestGemDependencyList < Gem::TestCase
   end
 
   def test_remove_by_name
-    util_clear_gems
-
     @deplist.add @a1, @b2
 
     @deplist.remove_by_name "a-1"
diff --git a/test/rubygems/test_gem_ext_builder.rb b/test/rubygems/test_gem_ext_builder.rb
index 46a4385750..7091acdca0 100644
--- a/test/rubygems/test_gem_ext_builder.rb
+++ b/test/rubygems/test_gem_ext_builder.rb
@@ -329,4 +329,4 @@ install:
     assert_equal %w[--with-foo-dir=/nonexistent], builder.build_args
   end
 
-end
+end unless Gem.java_platform?
diff --git a/test/rubygems/test_gem_ext_cmake_builder.rb b/test/rubygems/test_gem_ext_cmake_builder.rb
index 757266cae2..f7dc383fe9 100644
--- a/test/rubygems/test_gem_ext_cmake_builder.rb
+++ b/test/rubygems/test_gem_ext_cmake_builder.rb
@@ -10,6 +10,8 @@ class TestGemExtCmakeBuilder < Gem::TestCase
     # Details: https://github.com/rubygems/rubygems/issues/1270#issuecomment-177368340
     skip "CmakeBuilder doesn't work on Windows." if Gem.win_platform?
 
+    skip "CmakeBuilder doesn't work on JRuby." if Gem.java_platform? && ENV["CI"]
+
     system('cmake', out: IO::NULL, err: [:child, :out])
 
     skip 'cmake not present' unless $?.success?
diff --git a/test/rubygems/test_gem_ext_configure_builder.rb b/test/rubygems/test_gem_ext_configure_builder.rb
index 967458170b..eeeb654ae9 100644
--- a/test/rubygems/test_gem_ext_configure_builder.rb
+++ b/test/rubygems/test_gem_ext_configure_builder.rb
@@ -18,6 +18,10 @@ class TestGemExtConfigureBuilder < Gem::TestCase
   end
 
   def test_self_build
+    if java_platform? && ENV["CI"]
+      skip("failing on jruby")
+    end
+
     skip("test_self_build skipped on MS Windows (VC++)") if vc_windows?
 
     File.open File.join(@ext, './configure'), 'w' do |configure|
@@ -45,6 +49,10 @@ class TestGemExtConfigureBuilder < Gem::TestCase
   end
 
   def test_self_build_fail
+    if java_platform? && ENV["CI"]
+      skip("failing on jruby")
+    end
+
     skip("test_self_build_fail skipped on MS Windows (VC++)") if vc_windows?
     output = []
 
diff --git a/test/rubygems/test_gem_ext_ext_conf_builder.rb b/test/rubygems/test_gem_ext_ext_conf_builder.rb
index 6decb29a99..d92da46f92 100644
--- a/test/rubygems/test_gem_ext_ext_conf_builder.rb
+++ b/test/rubygems/test_gem_ext_ext_conf_builder.rb
@@ -17,6 +17,10 @@ class TestGemExtExtConfBuilder < Gem::TestCase
   end
 
   def test_class_build
+    if java_platform? && ENV["CI"]
+      skip("failing on jruby")
+    end
+
     if vc_windows? && !nmake_found?
       skip("test_class_build skipped - nmake not found")
     end
@@ -45,6 +49,10 @@ class TestGemExtExtConfBuilder < Gem::TestCase
   end
 
   def test_class_build_rbconfig_make_prog
+    if java_platform? && ENV["CI"]
+      skip("failing on jruby")
+    end
+
     configure_args do
 
       File.open File.join(@ext, 'extconf.rb'), 'w' do |extconf|
@@ -68,6 +76,10 @@ class TestGemExtExtConfBuilder < Gem::TestCase
     env_make = ENV.delete 'MAKE'
     ENV['MAKE'] = 'anothermake'
 
+    if java_platform? && ENV["CI"]
+      skip("failing on jruby")
+    end
+
     configure_args '' do
       File.open File.join(@ext, 'extconf.rb'), 'w' do |extconf|
         extconf.puts "require 'mkmf'\ncreate_makefile 'foo'"
diff --git a/test/rubygems/test_gem_indexer.rb b/test/rubygems/test_gem_indexer.rb
index ce08702c41..43a04c3bb3 100644
--- a/test/rubygems/test_gem_indexer.rb
+++ b/test/rubygems/test_gem_indexer.rb
@@ -11,7 +11,6 @@ class TestGemIndexer < Gem::TestCase
   def setup
     super
 
-    util_clear_gems
     util_make_gems
 
     @d2_0 = util_spec 'd', '2.0' do |s|
@@ -28,30 +27,23 @@ class TestGemIndexer < Gem::TestCase
     @default = new_default_spec 'default', 2
     install_default_gems @default
 
-    @tempdir = File.join(@tempdir, 'indexer')
+    @indexerdir = File.join(@tempdir, 'indexer')
 
-    gems = File.join(@tempdir, 'gems')
+    gems = File.join(@indexerdir, 'gems')
     FileUtils.mkdir_p gems
     FileUtils.mv Dir[File.join(@gemhome, "cache", '*.gem')], gems
 
-    @indexer = Gem::Indexer.new(@tempdir)
-  end
-
-  def teardown
-    super
-
-    util_clear_gems
-    util_clear_default_gems
+    @indexer = Gem::Indexer.new(@indexerdir)
   end
 
   def test_initialize
-    assert_equal @tempdir, @indexer.dest_directory
+    assert_equal @indexerdir, @indexer.dest_directory
     assert_match %r{#{Dir.mktmpdir('gem_generate_index').match(/.*-/)}}, @indexer.directory
 
-    indexer = Gem::Indexer.new @tempdir
+    indexer = Gem::Indexer.new @indexerdir
     assert indexer.build_modern
 
-    indexer = Gem::Indexer.new @tempdir, :build_modern => true
+    indexer = Gem::Indexer.new @indexerdir, :build_modern => true
     assert indexer.build_modern
   end
 
@@ -100,7 +92,7 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    quickdir = File.join @tempdir, 'quick'
+    quickdir = File.join @indexerdir, 'quick'
     marshal_quickdir = File.join quickdir, "Marshal.#{@marshal_version}"
 
     assert_directory_exists quickdir
@@ -111,11 +103,11 @@ class TestGemIndexer < Gem::TestCase
 
     refute_indexed marshal_quickdir, File.basename(@c1_2.spec_file)
 
-    assert_indexed @tempdir, "specs.#{@marshal_version}"
-    assert_indexed @tempdir, "specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}.gz"
 
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}"
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}.gz"
   end
 
   def test_generate_index_modern
@@ -125,12 +117,12 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    refute_indexed @tempdir, 'yaml'
-    refute_indexed @tempdir, 'yaml.Z'
-    refute_indexed @tempdir, "Marshal.#{@marshal_version}"
-    refute_indexed @tempdir, "Marshal.#{@marshal_version}.Z"
+    refute_indexed @indexerdir, 'yaml'
+    refute_indexed @indexerdir, 'yaml.Z'
+    refute_indexed @indexerdir, "Marshal.#{@marshal_version}"
+    refute_indexed @indexerdir, "Marshal.#{@marshal_version}.Z"
 
-    quickdir = File.join @tempdir, 'quick'
+    quickdir = File.join @indexerdir, 'quick'
     marshal_quickdir = File.join quickdir, "Marshal.#{@marshal_version}"
 
     assert_directory_exists quickdir, 'quickdir should be directory'
@@ -156,11 +148,11 @@ class TestGemIndexer < Gem::TestCase
     refute_indexed quickdir, "#{File.basename(@c1_2.spec_file)}"
     refute_indexed marshal_quickdir, "#{File.basename(@c1_2.spec_file)}"
 
-    assert_indexed @tempdir, "specs.#{@marshal_version}"
-    assert_indexed @tempdir, "specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}.gz"
 
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}"
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}.gz"
   end
 
   def test_generate_index_modern_back_to_back
@@ -170,13 +162,13 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    @indexer = Gem::Indexer.new @tempdir
+    @indexer = Gem::Indexer.new @indexerdir
     @indexer.build_modern = true
 
     use_ui @ui do
       @indexer.generate_index
     end
-    quickdir = File.join @tempdir, 'quick'
+    quickdir = File.join @indexerdir, 'quick'
     marshal_quickdir = File.join quickdir, "Marshal.#{@marshal_version}"
 
     assert_directory_exists quickdir
@@ -185,11 +177,11 @@ class TestGemIndexer < Gem::TestCase
     assert_indexed marshal_quickdir, "#{File.basename(@a1.spec_file)}.rz"
     assert_indexed marshal_quickdir, "#{File.basename(@a2.spec_file)}.rz"
 
-    assert_indexed @tempdir, "specs.#{@marshal_version}"
-    assert_indexed @tempdir, "specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "specs.#{@marshal_version}.gz"
 
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}"
-    assert_indexed @tempdir, "latest_specs.#{@marshal_version}.gz"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}"
+    assert_indexed @indexerdir, "latest_specs.#{@marshal_version}.gz"
   end
 
   def test_generate_index_ui
@@ -215,7 +207,7 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    specs_path = File.join @tempdir, "specs.#{@marshal_version}"
+    specs_path = File.join @indexerdir, "specs.#{@marshal_version}"
 
     specs_dump = Gem.read_binary specs_path
     specs = Marshal.load specs_dump
@@ -252,7 +244,7 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    latest_specs_path = File.join @tempdir, "latest_specs.#{@marshal_version}"
+    latest_specs_path = File.join @indexerdir, "latest_specs.#{@marshal_version}"
 
     latest_specs_dump = Gem.read_binary latest_specs_path
     latest_specs = Marshal.load latest_specs_dump
@@ -282,7 +274,7 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    prerelease_specs_path = File.join @tempdir, "prerelease_specs.#{@marshal_version}"
+    prerelease_specs_path = File.join @indexerdir, "prerelease_specs.#{@marshal_version}"
 
     prerelease_specs_dump = Gem.read_binary prerelease_specs_path
     prerelease_specs = Marshal.load prerelease_specs_dump
@@ -311,7 +303,7 @@ class TestGemIndexer < Gem::TestCase
       @indexer.generate_index
     end
 
-    quickdir = File.join @tempdir, 'quick'
+    quickdir = File.join @indexerdir, 'quick'
     marshal_quickdir = File.join quickdir, "Marshal.#{@marshal_version}"
 
     assert_directory_exists quickdir
@@ -325,7 +317,7 @@ class TestGemIndexer < Gem::TestCase
     util_build_gem @d2_1_a
     @d2_1_a_tuple = [@d2_1_a.name, @d2_1_a.version, @d2_1_a.original_platform]
 
-    gems = File.join @tempdir, 'gems'
+    gems = File.join @indexerdir, 'gems'
 
     FileUtils.mv @d2_1.cache_file, gems
     FileUtils.mv @d2_1_a.cache_file, gems
diff --git a/test/rubygems/test_gem_install_update_options.rb b/test/rubygems/test_gem_install_update_options.rb
index dd6bd08dde..c6b4778336 100644
--- a/test/rubygems/test_gem_install_update_options.rb
+++ b/test/rubygems/test_gem_install_update_options.rb
@@ -26,10 +26,11 @@ class TestGemInstallUpdateOptions < Gem::InstallerTestCase
       -f
       -i /install_to
       -w
-      --vendor
       --post-install-message
     ]
 
+    args.concat %w[--vendor] unless Gem.java_platform?
+
     args.concat %w[-P HighSecurity] if defined?(OpenSSL::SSL)
 
     assert @cmd.handles?(args)
@@ -111,6 +112,13 @@ class TestGemInstallUpdateOptions < Gem::InstallerTestCase
   end
 
   def test_user_install_enabled
+    @spec = quick_gem 'a' do |spec|
+      util_make_exec spec
+    end
+
+    util_build_gem @spec
+    @gem = @spec.cache_file
+
     @cmd.handle_options %w[--user-install]
 
     assert @cmd.options[:user_install]
@@ -122,6 +130,13 @@ class TestGemInstallUpdateOptions < Gem::InstallerTestCase
   end
 
   def test_user_install_disabled_read_only
+    @spec = quick_gem 'a' do |spec|
+      util_make_exec spec
+    end
+
+    util_build_gem @spec
+    @gem = @spec.cache_file
+
     if win_platform?
       skip('test_user_install_disabled_read_only test skipped on MS Windows')
     elsif Process.uid.zero?
@@ -145,28 +160,26 @@ class TestGemInstallUpdateOptions < Gem::InstallerTestCase
   end
 
   def test_vendor
-    @cmd.handle_options %w[--vendor]
+    vendordir(File.join(@tempdir, 'vendor')) do
+      @cmd.handle_options %w[--vendor]
 
-    assert @cmd.options[:vendor]
-    assert_equal Gem.vendor_dir, @cmd.options[:install_dir]
+      assert @cmd.options[:vendor]
+      assert_equal Gem.vendor_dir, @cmd.options[:install_dir]
+    end
   end
 
   def test_vendor_missing
-    orig_vendordir = RbConfig::CONFIG['vendordir']
-    RbConfig::CONFIG.delete 'vendordir'
-
-    e = assert_raises OptionParser::InvalidOption do
-      @cmd.handle_options %w[--vendor]
-    end
-
-    assert_equal 'invalid option: --vendor your platform is not supported',
-                 e.message
+    vendordir(nil) do
+      e = assert_raises OptionParser::InvalidOption do
+        @cmd.handle_options %w[--vendor]
+      end
 
-    refute @cmd.options[:vendor]
-    refute @cmd.options[:install_dir]
+      assert_equal 'invalid option: --vendor your platform is not supported',
+                   e.message
 
-  ensure
-    RbConfig::CONFIG['vendordir'] = orig_vendordir
+      refute @cmd.options[:vendor]
+      refute @cmd.options[:install_dir]
+    end
   end
 
   def test_post_install_message_no
diff --git a/test/rubygems/test_gem_installer.rb b/test/rubygems/test_gem_installer.rb
index 7f325080ec..0e611b60ea 100644
--- a/test/rubygems/test_gem_installer.rb
+++ b/test/rubygems/test_gem_installer.rb
@@ -22,11 +22,6 @@ class TestGemInstaller < Gem::InstallerTestCase
     super
     common_installer_setup
 
-    if (self.class.method_defined?(:__name__) ? __name__ : name) =~ /\Atest_install(_|\Z)/
-      FileUtils.rm_r @spec.gem_dir
-      FileUtils.rm_r @user_spec.gem_dir
-    end
-
     @config = Gem.configuration
   end
 
@@ -39,6 +34,8 @@ class TestGemInstaller < Gem::InstallerTestCase
   end
 
   def test_app_script_text
+    installer = setup_base_installer
+
     util_make_exec @spec, ''
 
     expected = <<-EOF
@@ -71,12 +68,14 @@ load Gem.bin_path("a", "executable", version)
 end
     EOF
 
-    wrapper = @installer.app_script_text 'executable'
+    wrapper = installer.app_script_text 'executable'
     assert_equal expected, wrapper
   end
 
   def test_check_executable_overwrite
-    @installer.generate_bin
+    installer = setup_base_installer
+
+    installer.generate_bin
 
     @spec = Gem::Specification.new do |s|
       s.files = ['lib/code.rb']
@@ -88,9 +87,9 @@ end
     end
 
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
-    @installer.wrappers = true
-    @installer.generate_bin
+    installer.gem_dir = @spec.gem_dir
+    installer.wrappers = true
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -100,6 +99,8 @@ end
   end
 
   def test_check_executable_overwrite_default_bin_dir
+    installer = setup_base_installer
+
     if defined?(RUBY_FRAMEWORK_VERSION)
       orig_RUBY_FRAMEWORK_VERSION = RUBY_FRAMEWORK_VERSION
       Object.send :remove_const, :RUBY_FRAMEWORK_VERSION
@@ -112,7 +113,7 @@ end
     ui = Gem::MockGemUi.new "n\n"
     use_ui ui do
       e = assert_raises Gem::InstallError do
-        @installer.generate_bin
+        installer.generate_bin
       end
 
       conflicted = File.join @gemhome, 'bin', 'executable'
@@ -130,7 +131,9 @@ end
   end
 
   def test_check_executable_overwrite_format_executable
-    @installer.generate_bin
+    installer = setup_base_installer
+
+    installer.generate_bin
 
     @spec = Gem::Specification.new do |s|
       s.files = ['lib/code.rb']
@@ -153,11 +156,11 @@ gem 'other', version
 
     util_make_exec
     Gem::Installer.exec_format = 'foo-%s-bar'
-    @installer.gem_dir = @spec.gem_dir
-    @installer.wrappers = true
-    @installer.format_executable = true
+    installer.gem_dir = @spec.gem_dir
+    installer.wrappers = true
+    installer.format_executable = true
 
-    @installer.generate_bin # should not raise
+    installer.generate_bin # should not raise
 
     installed_exec = File.join util_inst_bindir, 'foo-executable-bar'
     assert_path_exists installed_exec
@@ -169,13 +172,15 @@ gem 'other', version
   end
 
   def test_check_executable_overwrite_other_gem
+    installer = setup_base_installer
+
     util_conflict_executable true
 
     ui = Gem::MockGemUi.new "n\n"
 
     use_ui ui do
       e = assert_raises Gem::InstallError do
-        @installer.generate_bin
+        installer.generate_bin
       end
 
       assert_equal '"executable" from a conflicts with installed executable from conflict',
@@ -184,11 +189,13 @@ gem 'other', version
   end
 
   def test_check_executable_overwrite_other_gem_force
+    installer = setup_base_installer
+
     util_conflict_executable true
-    @installer.wrappers = true
-    @installer.force = true
+    installer.wrappers = true
+    installer.force = true
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -198,10 +205,12 @@ gem 'other', version
   end
 
   def test_check_executable_overwrite_other_non_gem
+    installer = setup_base_installer
+
     util_conflict_executable false
-    @installer.wrappers = true
+    installer.wrappers = true
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -211,7 +220,9 @@ gem 'other', version
   end unless Gem.win_platform?
 
   def test_check_that_user_bin_dir_is_in_path
-    bin_dir = @installer.bin_dir
+    installer = setup_base_installer
+
+    bin_dir = installer.bin_dir
 
     if Gem.win_platform?
       bin_dir = bin_dir.downcase.gsub(File::SEPARATOR, File::ALT_SEPARATOR)
@@ -221,7 +232,7 @@ gem 'other', version
       ENV['PATH'], [ENV['PATH'], bin_dir].join(File::PATH_SEPARATOR)
 
     use_ui @ui do
-      @installer.check_that_user_bin_dir_is_in_path
+      installer.check_that_user_bin_dir_is_in_path
     end
 
     assert_empty @ui.error
@@ -235,10 +246,11 @@ gem 'other', version
     orig_PATH, ENV['PATH'] =
       ENV['PATH'], [ENV['PATH'], '~/bin'].join(File::PATH_SEPARATOR)
 
-    @installer.bin_dir.replace File.join @userhome, 'bin'
+    installer = setup_base_installer
+    installer.bin_dir.replace File.join @userhome, 'bin'
 
     use_ui @ui do
-      @installer.check_that_user_bin_dir_is_in_path
+      installer.check_that_user_bin_dir_is_in_path
     end
 
     assert_empty @ui.error
@@ -247,11 +259,13 @@ gem 'other', version
   end
 
   def test_check_that_user_bin_dir_is_in_path_not_in_path
+    installer = setup_base_installer
+
     use_ui @ui do
-      @installer.check_that_user_bin_dir_is_in_path
+      installer.check_that_user_bin_dir_is_in_path
     end
 
-    expected = @installer.bin_dir
+    expected = installer.bin_dir
 
     if Gem.win_platform?
       expected = expected.downcase.gsub(File::SEPARATOR, File::ALT_SEPARATOR)
@@ -261,14 +275,16 @@ gem 'other', version
   end
 
   def test_ensure_dependency
+    installer = setup_base_installer
+
     util_spec 'a'
 
     dep = Gem::Dependency.new 'a', '>= 2'
-    assert @installer.ensure_dependency(@spec, dep)
+    assert installer.ensure_dependency(@spec, dep)
 
     dep = Gem::Dependency.new 'b', '> 2'
     e = assert_raises Gem::InstallError do
-      @installer.ensure_dependency @spec, dep
+      installer.ensure_dependency @spec, dep
     end
 
     assert_equal 'a requires b (> 2)', e.message
@@ -305,26 +321,30 @@ gem 'other', version
   end
 
   def test_extract_files
-    @installer.extract_files
+    installer = setup_base_installer
+
+    installer.extract_files
 
     assert_path_exists File.join @spec.gem_dir, 'bin/executable'
   end
 
   def test_generate_bin_bindir
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
 
     @spec.executables = %w[executable]
     @spec.bindir = 'bin'
 
-    exec_file = @installer.formatted_program_filename 'executable'
+    exec_file = installer.formatted_program_filename 'executable'
     exec_path = File.join @spec.gem_dir, exec_file
     File.open exec_path, 'w' do |f|
       f.puts '#!/usr/bin/ruby'
     end
 
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
 
     assert_directory_exists util_inst_bindir
     installed_exec = File.join(util_inst_bindir, 'executable')
@@ -362,11 +382,13 @@ gem 'other', version
   end
 
   def test_generate_bin_script
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
     assert_directory_exists util_inst_bindir
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -377,13 +399,15 @@ gem 'other', version
   end
 
   def test_generate_bin_script_format
-    @installer.format_executable = true
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.format_executable = true
+    installer.wrappers = true
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
     Gem::Installer.exec_format = 'foo-%s-bar'
-    @installer.generate_bin
+    installer.generate_bin
     assert_directory_exists util_inst_bindir
     installed_exec = File.join util_inst_bindir, 'foo-executable-bar'
     assert_path_exists installed_exec
@@ -392,12 +416,14 @@ gem 'other', version
   end
 
   def test_generate_bin_script_format_disabled
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
     Gem::Installer.exec_format = 'foo-%s-bar'
-    @installer.generate_bin
+    installer.generate_bin
     assert_directory_exists util_inst_bindir
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -406,7 +432,9 @@ gem 'other', version
   end
 
   def test_generate_bin_script_install_dir
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
 
     gem_dir = File.join("#{@gemhome}2", "gems", @spec.full_name)
     gem_bindir = File.join gem_dir, 'bin'
@@ -415,11 +443,11 @@ gem 'other', version
       f.puts "#!/bin/ruby"
     end
 
-    @installer.gem_home = "#{@gemhome}2"
-    @installer.gem_dir = gem_dir
-    @installer.bin_dir = File.join "#{@gemhome}2", 'bin'
+    installer.gem_home = "#{@gemhome}2"
+    installer.gem_dir = gem_dir
+    installer.bin_dir = File.join "#{@gemhome}2", 'bin'
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join("#{@gemhome}2", "bin", 'executable')
     assert_path_exists installed_exec
@@ -430,16 +458,20 @@ gem 'other', version
   end
 
   def test_generate_bin_script_no_execs
-    util_execless
+    installer = setup_base_installer
 
-    @installer.wrappers = true
-    @installer.generate_bin
+    installer = util_execless
+
+    installer.wrappers = true
+    installer.generate_bin
 
     refute_path_exists util_inst_bindir, 'bin dir was created when not needed'
   end
 
   def test_generate_bin_script_no_perms
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
 
     Dir.mkdir util_inst_bindir
@@ -452,7 +484,7 @@ gem 'other', version
       FileUtils.chmod 0000, util_inst_bindir
 
       assert_raises Gem::FilePermissionError do
-        @installer.generate_bin
+        installer.generate_bin
       end
     end
   ensure
@@ -460,7 +492,9 @@ gem 'other', version
   end
 
   def test_generate_bin_script_no_shebang
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     @spec.executables = %w[executable]
 
     gem_dir = File.join @gemhome, 'gems', @spec.full_name
@@ -470,7 +504,7 @@ gem 'other', version
       f.puts "blah blah blah"
     end
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join @gemhome, 'bin', 'executable'
     assert_path_exists installed_exec
@@ -483,9 +517,11 @@ gem 'other', version
   end
 
   def test_generate_bin_script_wrappers
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
     installed_exec = File.join(util_inst_bindir, 'executable')
 
     real_exec = File.join @spec.gem_dir, 'bin', 'executable'
@@ -496,7 +532,7 @@ gem 'other', version
       FileUtils.ln_s real_exec, installed_exec
     end
 
-    @installer.generate_bin
+    installer.generate_bin
     assert_directory_exists util_inst_bindir
     assert_path_exists installed_exec
     assert_equal mask, File.stat(installed_exec).mode unless win_platform?
@@ -510,11 +546,13 @@ gem 'other', version
   def test_generate_bin_symlink
     return if win_platform? #Windows FS do not support symlinks
 
-    @installer.wrappers = false
+    installer = setup_base_installer
+
+    installer.wrappers = false
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
     assert_directory_exists util_inst_bindir
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_equal true, File.symlink?(installed_exec)
@@ -523,18 +561,22 @@ gem 'other', version
   end
 
   def test_generate_bin_symlink_no_execs
-    util_execless
+    installer = setup_base_installer
+
+    installer = util_execless
 
-    @installer.wrappers = false
-    @installer.generate_bin
+    installer.wrappers = false
+    installer.generate_bin
 
     refute_path_exists util_inst_bindir
   end
 
   def test_generate_bin_symlink_no_perms
-    @installer.wrappers = false
+    installer = setup_base_installer
+
+    installer.wrappers = false
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
     Dir.mkdir util_inst_bindir
 
@@ -546,7 +588,7 @@ gem 'other', version
       FileUtils.chmod 0000, util_inst_bindir
 
       assert_raises Gem::FilePermissionError do
-        @installer.generate_bin
+        installer.generate_bin
       end
     end
   ensure
@@ -556,11 +598,13 @@ gem 'other', version
   def test_generate_bin_symlink_update_newer
     return if win_platform? #Windows FS do not support symlinks
 
-    @installer.wrappers = false
+    installer = setup_base_installer
+
+    installer.wrappers = false
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
     installed_exec = File.join(util_inst_bindir, 'executable')
     assert_equal(File.join(@spec.gem_dir, 'bin', 'executable'),
                  File.readlink(installed_exec))
@@ -575,8 +619,8 @@ gem 'other', version
     end
 
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
-    @installer.generate_bin
+    installer.gem_dir = @spec.gem_dir
+    installer.generate_bin
     installed_exec = File.join(util_inst_bindir, 'executable')
     assert_equal(@spec.bin_file('executable'),
                  File.readlink(installed_exec),
@@ -586,11 +630,13 @@ gem 'other', version
   def test_generate_bin_symlink_update_older
     return if !symlink_supported?
 
-    @installer.wrappers = false
+    installer = setup_base_installer
+
+    installer.wrappers = false
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
     installed_exec = File.join(util_inst_bindir, 'executable')
     assert_equal(File.join(@spec.gem_dir, 'bin', 'executable'),
                  File.readlink(installed_exec))
@@ -607,10 +653,10 @@ gem 'other', version
     util_make_exec
     one = @spec.dup
     one.version = 1
-    @installer = Gem::Installer.for_spec spec
-    @installer.gem_dir = one.gem_dir
+    installer = Gem::Installer.for_spec spec
+    installer.gem_dir = one.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     expected = File.join @spec.gem_dir, 'bin', 'executable'
@@ -622,11 +668,13 @@ gem 'other', version
   def test_generate_bin_symlink_update_remove_wrapper
     return if !symlink_supported?
 
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_path_exists installed_exec
@@ -642,10 +690,10 @@ gem 'other', version
     util_make_exec
 
     util_installer @spec, @gemhome
-    @installer.wrappers = false
-    @installer.gem_dir = @spec.gem_dir
+    installer.wrappers = false
+    installer.gem_dir = @spec.gem_dir
 
-    @installer.generate_bin
+    installer.generate_bin
 
     installed_exec = File.join util_inst_bindir, 'executable'
     assert_equal(@spec.bin_file('executable'),
@@ -659,12 +707,15 @@ gem 'other', version
     old_alt_separator = File::ALT_SEPARATOR
     File.__send__(:remove_const, :ALT_SEPARATOR)
     File.const_set(:ALT_SEPARATOR, '\\')
-    @installer.wrappers = false
+
+    installer = setup_base_installer
+
+    installer.wrappers = false
     util_make_exec
-    @installer.gem_dir = @spec.gem_dir
+    installer.gem_dir = @spec.gem_dir
 
     use_ui @ui do
-      @installer.generate_bin
+      installer.generate_bin
     end
 
     assert_directory_exists util_inst_bindir
@@ -690,10 +741,12 @@ gem 'other', version
   def test_generate_bin_uses_default_shebang
     return if !symlink_supported?
 
-    @installer.wrappers = true
+    installer = setup_base_installer
+
+    installer.wrappers = true
     util_make_exec
 
-    @installer.generate_bin
+    installer.generate_bin
 
     default_shebang = Gem.ruby
     shebang_line = open("#{@gemhome}/bin/executable") { |f| f.readlines.first }
@@ -719,6 +772,8 @@ gem 'other', version
   end
 
   def test_initialize_user_install
+    @gem = setup_base_gem
+
     installer = Gem::Installer.at @gem, :user_install => true
 
     assert_equal File.join(Gem.user_dir, 'gems', @spec.full_name),
@@ -727,6 +782,8 @@ gem 'other', version
   end
 
   def test_initialize_user_install_bin_dir
+    @gem = setup_base_gem
+
     installer =
       Gem::Installer.at @gem, :user_install => true, :bin_dir => @tempdir
 
@@ -736,9 +793,7 @@ gem 'other', version
   end
 
   def test_install
-    Dir.mkdir util_inst_bindir
-    util_setup_gem
-    util_clear_gems
+    installer = util_setup_installer
 
     gemdir     = File.join @gemhome, 'gems', @spec.full_name
     cache_file = File.join @gemhome, 'cache', @spec.file_name
@@ -746,13 +801,13 @@ gem 'other', version
     rakefile   = File.join gemdir, 'ext', 'a', 'Rakefile'
     spec_file  = File.join @gemhome, 'specifications', @spec.spec_name
 
-    Gem.pre_install do |installer|
+    Gem.pre_install do
       refute_path_exists cache_file, 'cache file must not exist yet'
       refute_path_exists spec_file,  'spec file must not exist yet'
       true
     end
 
-    Gem.post_build do |installer|
+    Gem.post_build do
       assert_path_exists gemdir, 'gem install dir must exist'
       assert_path_exists rakefile, 'gem executable must exist'
       refute_path_exists stub_exe, 'gem executable must not exist'
@@ -760,7 +815,7 @@ gem 'other', version
       true
     end
 
-    Gem.post_install do |installer|
+    Gem.post_install do
       assert_path_exists cache_file, 'cache file must exist'
       assert_path_exists spec_file,  'spec file must exist'
     end
@@ -768,7 +823,7 @@ gem 'other', version
     @newspec = nil
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -786,29 +841,25 @@ gem 'other', version
 
     assert_path_exists rakefile
 
-    spec_file = File.join(@gemhome, 'specifications', @spec.spec_name)
-
     assert_equal spec_file, @newspec.loaded_from
     assert_path_exists spec_file
 
-    assert_same @installer, @post_build_hook_arg
-    assert_same @installer, @post_install_hook_arg
-    assert_same @installer, @pre_install_hook_arg
+    assert_same installer, @post_build_hook_arg
+    assert_same installer, @post_install_hook_arg
+    assert_same installer, @pre_install_hook_arg
   end
 
   def test_install_creates_working_binstub
-    Dir.mkdir util_inst_bindir
-    util_setup_gem
-    util_clear_gems
+    installer = util_setup_installer
 
-    @installer.wrappers = true
+    installer.wrappers = true
 
     gemdir = File.join @gemhome, 'gems', @spec.full_name
 
     @newspec = nil
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -822,11 +873,10 @@ gem 'other', version
   end
 
   def test_conflicting_binstubs
-    Dir.mkdir util_inst_bindir
-    util_clear_gems
+    @gem = setup_base_gem
 
     # build old version that has a bin file
-    util_setup_gem do |spec|
+    installer = util_setup_gem do |spec|
       File.open File.join('bin', 'executable'), 'w' do |f|
         f.puts "require 'code'"
       end
@@ -835,17 +885,17 @@ gem 'other', version
       end
     end
 
-    @installer.wrappers = true
+    installer.wrappers = true
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
-    old_bin_file = File.join @installer.bin_dir, 'executable'
+    old_bin_file = File.join installer.bin_dir, 'executable'
 
     # build new version that doesn't have a bin file
-    util_setup_gem do |spec|
+    installer = util_setup_gem do |spec|
       FileUtils.rm File.join('bin', 'executable')
       spec.files.delete File.join('bin', 'executable')
       spec.executables.delete 'executable'
@@ -857,7 +907,7 @@ gem 'other', version
 
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -871,16 +921,14 @@ gem 'other', version
   end
 
   def test_install_creates_binstub_that_understand_version
-    Dir.mkdir util_inst_bindir
-    util_setup_gem
-    util_clear_gems
+    installer = util_setup_installer
 
-    @installer.wrappers = true
+    installer.wrappers = true
 
     @newspec = nil
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -902,23 +950,21 @@ gem 'other', version
   end
 
   def test_install_creates_binstub_that_prefers_user_installed_gem_to_default
-    Dir.mkdir util_inst_bindir
-
     install_default_gems new_default_spec('default', '2')
 
-    util_setup_gem do |spec|
+    installer = util_setup_installer do |spec|
       spec.name = 'default'
       spec.version = '2'
     end
 
     util_clear_gems
 
-    @installer.wrappers = true
+    installer.wrappers = true
 
     @newspec = nil
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -932,16 +978,14 @@ gem 'other', version
   end
 
   def test_install_creates_binstub_that_dont_trust_encoding
-    Dir.mkdir util_inst_bindir
-    util_setup_gem
-    util_clear_gems
+    installer = util_setup_installer
 
-    @installer.wrappers = true
+    installer.wrappers = true
 
     @newspec = nil
     build_rake_in do
       use_ui @ui do
-        @newspec = @installer.install
+        @newspec = installer.install
       end
     end
 
@@ -964,20 +1008,19 @@ gem 'other', version
   end
 
   def test_install_with_no_prior_files
-    Dir.mkdir util_inst_bindir
-    util_clear_gems
+    installer = util_setup_installer
 
-    util_setup_gem
     build_rake_in do
       use_ui @ui do
-        assert_equal @spec, @installer.install
+        assert_equal @spec, installer.install
       end
     end
 
     gemdir = File.join(@gemhome, 'gems', @spec.full_name)
     assert_path_exists File.join gemdir, 'lib', 'code.rb'
 
-    util_setup_gem
+    installer = util_setup_installer
+
     # Morph spec to have lib/other.rb instead of code.rb and recreate
     @spec.files = File.join('lib', 'other.rb')
     Dir.chdir @tempdir do
@@ -990,10 +1033,10 @@ gem 'other', version
         Gem::Package.build @spec
       end
     end
-    @installer = Gem::Installer.at @gem
+    installer = Gem::Installer.at @gem
     build_rake_in do
       use_ui @ui do
-        assert_equal @spec, @installer.install
+        assert_equal @spec, installer.install
       end
     end
 
@@ -1013,12 +1056,14 @@ gem 'other', version
   end
 
   def test_install_missing_dirs
+    installer = setup_base_installer
+
     FileUtils.rm_f File.join(Gem.dir, 'cache')
     FileUtils.rm_f File.join(Gem.dir, 'doc')
     FileUtils.rm_f File.join(Gem.dir, 'specifications')
 
     use_ui @ui do
-      @installer.install
+      installer.install
     end
 
     assert_directory_exists File.join(Gem.dir, 'cache')
@@ -1030,7 +1075,7 @@ gem 'other', version
   end
 
   def test_install_post_build_false
-    util_clear_gems
+    installer = setup_base_installer
 
     Gem.post_build do
       false
@@ -1038,7 +1083,7 @@ gem 'other', version
 
     use_ui @ui do
       e = assert_raises Gem::InstallError do
-        @installer.install
+        installer.install
       end
 
       location = "#{__FILE__}:#{__LINE__ - 9}"
@@ -1054,14 +1099,14 @@ gem 'other', version
   end
 
   def test_install_post_build_nil
-    util_clear_gems
+    installer = setup_base_installer
 
     Gem.post_build do
       nil
     end
 
     use_ui @ui do
-      @installer.install
+      installer.install
     end
 
     spec_file = File.join @gemhome, 'specifications', @spec.spec_name
@@ -1072,7 +1117,7 @@ gem 'other', version
   end
 
   def test_install_pre_install_false
-    util_clear_gems
+    installer = setup_base_installer
 
     Gem.pre_install do
       false
@@ -1080,7 +1125,7 @@ gem 'other', version
 
     use_ui @ui do
       e = assert_raises Gem::InstallError do
-        @installer.install
+        installer.install
       end
 
       location = "#{__FILE__}:#{__LINE__ - 9}"
@@ -1093,14 +1138,14 @@ gem 'other', version
   end
 
   def test_install_pre_install_nil
-    util_clear_gems
+    installer = setup_base_installer
 
     Gem.pre_install do
       nil
     end
 
     use_ui @ui do
-      @installer.install
+      installer.install
     end
 
     spec_file = File.join @gemhome, 'specifications', @spec.spec_name
@@ -1108,26 +1153,28 @@ gem 'other', version
   end
 
   def test_install_with_message
+    @spec = setup_base_spec
     @spec.post_install_message = 'I am a shiny gem!'
 
     use_ui @ui do
       path = Gem::Package.build @spec
 
-      @installer = Gem::Installer.at path
-      @installer.install
+      installer = Gem::Installer.at path
+      installer.install
     end
 
     assert_match %r|I am a shiny gem!|, @ui.output
   end
 
   def test_install_with_skipped_message
+    @spec = setup_base_spec
     @spec.post_install_message = 'I am a shiny gem!'
 
     use_ui @ui do
       path = Gem::Package.build @spec
 
-      @installer = Gem::Installer.at path, :post_install_message => false
-      @installer.install
+      installer = Gem::Installer.at path, :post_install_message => false
+      installer.install
     end
 
     refute_match %r|I am a shiny gem!|, @ui.output
@@ -1136,6 +1183,7 @@ gem 'other', version
   def test_install_extension_dir
     gemhome2 = "#{@gemhome}2"
 
+    @spec = setup_base_spec
     @spec.extensions << "extconf.rb"
     write_file File.join(@tempdir, "extconf.rb") do |io|
       io.write <<-RUBY
@@ -1159,6 +1207,8 @@ gem 'other', version
   end
 
   def test_install_extension_dir_is_removed_on_reinstall
+    @spec = setup_base_spec
+
     @spec.extensions << "extconf.rb"
     write_file File.join(@tempdir, "extconf.rb") do |io|
       io.write <<-RUBY
@@ -1194,6 +1244,7 @@ gem 'other', version
   end
 
   def test_install_user_extension_dir
+    @spec = setup_base_spec
     @spec.extensions << "extconf.rb"
     write_file File.join(@tempdir, "extconf.rb") do |io|
       io.write <<-RUBY
@@ -1223,6 +1274,9 @@ gem 'other', version
   end
 
   def test_find_lib_file_after_install
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
+
+    @spec = setup_base_spec
     @spec.extensions << "extconf.rb"
     write_file File.join(@tempdir, "extconf.rb") do |io|
       io.write <<-RUBY
@@ -1266,6 +1320,9 @@ gem 'other', version
   end
 
   def test_install_extension_and_script
+    skip "Makefile creation crashes on jruby" if Gem.java_platform?
+
+    @spec = setup_base_spec
     @spec.extensions << "extconf.rb"
     write_file File.join(@tempdir, "extconf.rb") do |io|
       io.write <<-RUBY
@@ -1296,14 +1353,17 @@ gem 'other', version
     use_ui @ui do
       path = Gem::Package.build @spec
 
-      @installer = Gem::Installer.at path
-      @installer.install
+      installer = Gem::Installer.at path
+      installer.install
     end
     assert_path_exists File.join @spec.gem_dir, rb
     assert_path_exists File.join @spec.gem_dir, rb2
   end
 
   def test_install_extension_flat
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
+
+    @spec = setup_base_spec
     @spec.require_paths = ["."]
 
     @spec.extensions << "extconf.rb"
@@ -1330,8 +1390,8 @@ gem 'other', version
     use_ui @ui do
       path = Gem::Package.build @spec
 
-      @installer = Gem::Installer.at path
-      @installer.install
+      installer = Gem::Installer.at path
+      installer.install
     end
     assert_path_exists so
   rescue
@@ -1350,49 +1410,56 @@ gem 'other', version
   end
 
   def test_installation_satisfies_dependency_eh
+    installer = setup_base_installer
+
     util_spec 'a'
 
     dep = Gem::Dependency.new 'a', '>= 2'
-    assert @installer.installation_satisfies_dependency?(dep)
+    assert installer.installation_satisfies_dependency?(dep)
 
     dep = Gem::Dependency.new 'a', '> 2'
-    refute @installer.installation_satisfies_dependency?(dep)
+    refute installer.installation_satisfies_dependency?(dep)
   end
 
   def test_installation_satisfies_dependency_eh_development
-    @installer.options[:development] = true
-    @installer.options[:dev_shallow] = true
+    installer = setup_base_installer
+    installer.options[:development] = true
+    installer.options[:dev_shallow] = true
 
     util_spec 'a'
 
     dep = Gem::Dependency.new 'a', :development
-    assert @installer.installation_satisfies_dependency?(dep)
+    assert installer.installation_satisfies_dependency?(dep)
   end
 
   def test_pre_install_checks_dependencies
+    installer = setup_base_installer
     @spec.add_dependency 'b', '> 5'
-    util_setup_gem
+    installer = util_setup_gem
 
     use_ui @ui do
       assert_raises Gem::InstallError do
-        @installer.install
+        installer.install
       end
     end
   end
 
   def test_pre_install_checks_dependencies_ignore
+    installer = util_setup_installer
     @spec.add_dependency 'b', '> 5'
-    @installer.ignore_dependencies = true
+    installer.ignore_dependencies = true
 
     build_rake_in do
       use_ui @ui do
-        assert @installer.pre_install_checks
+        assert installer.pre_install_checks
       end
     end
   end
 
   def test_pre_install_checks_dependencies_install_dir
     gemhome2 = "#{@gemhome}2"
+
+    @gem = setup_base_gem
     @spec.add_dependency 'd'
 
     quick_gem 'd', 2
@@ -1455,9 +1522,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::RuntimeRequirementNotMetError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       rgv = Gem::VERSION
       assert_equal "old_rubygems_required requires RubyGems version < 0. The current RubyGems version is #{rgv}. " +
@@ -1477,9 +1544,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal '#<Gem::Specification name=../malicious version=1> has an invalid name', e.message
     end
@@ -1497,9 +1564,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal "#<Gem::Specification name=malicious\n::Object.const_set(:FROM_EVAL, true)# version=1> has an invalid name", e.message
     end
@@ -1519,9 +1586,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal "#<Gem::Specification name=malicious version=1> has an invalid require_paths", e.message
     end
@@ -1542,9 +1609,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal "#<Gem::Specification name=malicious version=1> has an invalid extensions", e.message
     end
@@ -1563,9 +1630,9 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
+      installer = Gem::Installer.at gem
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal "#<Gem::Specification name=malicious version=1> has an invalid specification_version", e.message
     end
@@ -1584,75 +1651,90 @@ gem 'other', version
     gem = File.join(@gemhome, 'cache', spec.file_name)
 
     use_ui @ui do
-      @installer = Gem::Installer.at gem
-      @installer.ignore_dependencies = true
+      installer = Gem::Installer.at gem
+      installer.ignore_dependencies = true
       e = assert_raises Gem::InstallError do
-        @installer.pre_install_checks
+        installer.pre_install_checks
       end
       assert_equal "#<Gem::Specification name=malicious version=1> has an invalid dependencies", e.message
     end
   end
 
   def test_shebang
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/ruby"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_process_options
-    assert_nil @installer.build_root
-    assert_equal File.join(@gemhome, 'bin'), @installer.bin_dir
-    assert_equal @gemhome, @installer.gem_home
+    installer = setup_base_installer
+
+    assert_nil installer.build_root
+    assert_equal File.join(@gemhome, 'bin'), installer.bin_dir
+    assert_equal @gemhome, installer.gem_home
   end
 
   def test_process_options_build_root
     build_root = File.join @tempdir, 'build_root'
 
-    @installer = Gem::Installer.at @gem, :build_root => build_root
+    @gem = setup_base_gem
+    installer = Gem::Installer.at @gem, :build_root => build_root
 
-    assert_equal Pathname(build_root), @installer.build_root
-    assert_equal File.join(build_root, @gemhome, 'bin'), @installer.bin_dir
-    assert_equal File.join(build_root, @gemhome), @installer.gem_home
+    assert_equal Pathname(build_root), installer.build_root
+    assert_equal File.join(build_root, @gemhome, 'bin'), installer.bin_dir
+    assert_equal File.join(build_root, @gemhome), installer.gem_home
   end
 
   def test_shebang_arguments
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/ruby -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby} -ws", shebang
   end
 
   def test_shebang_empty
+    installer = setup_base_installer
+
     util_make_exec @spec, ''
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_shebang_env
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/env ruby"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_shebang_env_arguments
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/env ruby -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby} -ws", shebang
   end
 
   def test_shebang_env_shebang
+    installer = setup_base_installer
+
     util_make_exec @spec, ''
-    @installer.env_shebang = true
+    installer.env_shebang = true
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     env_shebang = "/usr/bin/env" unless Gem.win_platform?
 
@@ -1661,54 +1743,68 @@ gem 'other', version
   end
 
   def test_shebang_nested
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/opt/local/ruby/bin/ruby"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_shebang_nested_arguments
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/opt/local/ruby/bin/ruby -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby} -ws", shebang
   end
 
   def test_shebang_version
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/ruby18"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_shebang_version_arguments
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/ruby18 -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby} -ws", shebang
   end
 
   def test_shebang_version_env
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/env ruby18"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby}", shebang
   end
 
   def test_shebang_version_env_arguments
+    installer = setup_base_installer
+
     util_make_exec @spec, "#!/usr/bin/env ruby18 -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!#{Gem.ruby} -ws", shebang
   end
 
   def test_shebang_custom
+    installer = setup_base_installer
+
     conf = Gem::ConfigFile.new []
     conf[:custom_shebang] = 'test'
 
@@ -1716,12 +1812,14 @@ gem 'other', version
 
     util_make_exec @spec, "#!/usr/bin/ruby"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!test", shebang
   end
 
   def test_shebang_custom_with_expands
+    installer = setup_base_installer
+
     bin_env = win_platform? ? '' : '/usr/bin/env'
     conf = Gem::ConfigFile.new []
     conf[:custom_shebang] = '1 $env 2 $ruby 3 $exec 4 $name'
@@ -1730,12 +1828,14 @@ gem 'other', version
 
     util_make_exec @spec, "#!/usr/bin/ruby"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!1 #{bin_env} 2 #{Gem.ruby} 3 executable 4 a", shebang
   end
 
   def test_shebang_custom_with_expands_and_arguments
+    installer = setup_base_installer
+
     bin_env = win_platform? ? '' : '/usr/bin/env'
     conf = Gem::ConfigFile.new []
     conf[:custom_shebang] = '1 $env 2 $ruby 3 $exec'
@@ -1744,18 +1844,18 @@ gem 'other', version
 
     util_make_exec @spec, "#!/usr/bin/ruby -ws"
 
-    shebang = @installer.shebang 'executable'
+    shebang = installer.shebang 'executable'
 
     assert_equal "#!1 #{bin_env} 2 #{Gem.ruby} -ws 3 executable", shebang
   end
 
   def test_unpack
-    util_setup_gem
+    installer = util_setup_installer
 
     dest = File.join @gemhome, 'gems', @spec.full_name
 
     Gem::Deprecate.skip_during do
-      @installer.unpack dest
+      installer.unpack dest
     end
 
     assert_path_exists File.join dest, 'lib', 'code.rb'
@@ -1763,13 +1863,15 @@ gem 'other', version
   end
 
   def test_write_build_info_file
+    installer = setup_base_installer
+
     refute_path_exists @spec.build_info_file
 
-    @installer.build_args = %w[
+    installer.build_args = %w[
       --with-libyaml-dir /usr/local/Cellar/libyaml/0.1.4
     ]
 
-    @installer.write_build_info_file
+    installer.write_build_info_file
 
     assert_path_exists @spec.build_info_file
 
@@ -1779,14 +1881,17 @@ gem 'other', version
   end
 
   def test_write_build_info_file_empty
+    installer = setup_base_installer
+
     refute_path_exists @spec.build_info_file
 
-    @installer.write_build_info_file
+    installer.write_build_info_file
 
     refute_path_exists @spec.build_info_file
   end
 
   def test_write_build_info_file_install_dir
+    @gem = setup_base_gem
     installer = Gem::Installer.at @gem, :install_dir => "#{@gemhome}2"
 
     installer.build_args = %w[
@@ -1801,6 +1906,7 @@ gem 'other', version
   end
 
   def test_write_cache_file
+    @gem = setup_base_gem
     cache_file = File.join @gemhome, 'cache', @spec.file_name
     gem = File.join @gemhome, @spec.file_name
 
@@ -1816,13 +1922,14 @@ gem 'other', version
   end
 
   def test_write_spec
+    @spec = setup_base_spec
     FileUtils.rm @spec.spec_file
     refute_path_exists @spec.spec_file
 
-    @installer = Gem::Installer.for_spec @spec
-    @installer.gem_home = @gemhome
+    installer = Gem::Installer.for_spec @spec
+    installer.gem_home = @gemhome
 
-    @installer.write_spec
+    installer.write_spec
 
     assert_path_exists @spec.spec_file
 
@@ -1834,15 +1941,16 @@ gem 'other', version
   end
 
   def test_write_spec_writes_cached_spec
+    @spec = setup_base_spec
     FileUtils.rm @spec.spec_file
     refute_path_exists @spec.spec_file
 
     @spec.files = %w[a.rb b.rb c.rb]
 
-    @installer = Gem::Installer.for_spec @spec
-    @installer.gem_home = @gemhome
+    installer = Gem::Installer.for_spec @spec
+    installer.gem_home = @gemhome
 
-    @installer.write_spec
+    installer.write_spec
 
     # cached specs have no file manifest:
     @spec.files = []
@@ -1851,7 +1959,9 @@ gem 'other', version
   end
 
   def test_dir
-    assert_match %r!/gemhome/gems/a-2$!, @installer.dir
+    installer = setup_base_installer
+
+    assert_match %r!/gemhome/gems/a-2$!, installer.dir
   end
 
   def test_default_gem_loaded_from
@@ -1862,14 +1972,16 @@ gem 'other', version
   end
 
   def test_default_gem_without_wrappers
+    installer = setup_base_installer
+
     FileUtils.rm_f File.join(Gem.dir, 'specifications')
 
-    @installer.wrappers = false
-    @installer.options[:install_as_default] = true
-    @installer.gem_dir = @spec.gem_dir
+    installer.wrappers = false
+    installer.options[:install_as_default] = true
+    installer.gem_dir = @spec.gem_dir
 
     use_ui @ui do
-      @installer.install
+      installer.install
     end
 
     assert_directory_exists File.join(@spec.gem_dir, 'bin')
@@ -1893,14 +2005,14 @@ gem 'other', version
   end
 
   def test_default_gem_with_wrappers
-    FileUtils.rm_f File.join(Gem.dir, 'specifications')
+    installer = setup_base_installer
 
-    @installer.wrappers = true
-    @installer.options[:install_as_default] = true
-    @installer.gem_dir = @spec.gem_dir
+    installer.wrappers = true
+    installer.options[:install_as_default] = true
+    installer.gem_dir = @spec.gem_dir
 
     use_ui @ui do
-      @installer.install
+      installer.install
     end
 
     assert_directory_exists util_inst_bindir
@@ -1913,8 +2025,6 @@ gem 'other', version
   end
 
   def test_default_gem_with_exe_as_bindir
-    FileUtils.rm_f File.join(Gem.dir, 'specifications')
-
     @spec = quick_gem 'c' do |spec|
       util_make_exec spec, '#!/usr/bin/ruby', 'exe'
     end
@@ -1958,7 +2068,7 @@ gem 'other', version
     @spec = util_spec 'z'
     util_build_gem @spec
 
-    @installer = util_installer @spec, @gemhome
+    util_installer @spec, @gemhome
   end
 
   def util_conflict_executable(wrappers)
diff --git a/test/rubygems/test_gem_package.rb b/test/rubygems/test_gem_package.rb
index 03accc9dfe..cedd2f5e55 100644
--- a/test/rubygems/test_gem_package.rb
+++ b/test/rubygems/test_gem_package.rb
@@ -2,7 +2,6 @@
 # frozen_string_literal: true
 
 require 'rubygems/package/tar_test_case'
-require 'rubygems/simple_gem'
 
 class TestGemPackage < Gem::Package::TarTestCase
 
@@ -24,6 +23,8 @@ class TestGemPackage < Gem::Package::TarTestCase
   end
 
   def test_class_new_old_format
+    skip "jruby can't require the simple_gem file" if Gem.java_platform?
+    require_relative "simple_gem"
     File.open 'old_format.gem', 'wb' do |io|
       io.write SIMPLE_GEM
     end
@@ -839,6 +840,7 @@ class TestGemPackage < Gem::Package::TarTestCase
   end
 
   def test_verify_corrupt
+    skip "jruby strips the null byte and does not think it's corrupt" if Gem.java_platform?
     tf = Tempfile.open 'corrupt' do |io|
       data = Gem::Util.gzip 'a' * 10
       io.write \
diff --git a/test/rubygems/test_gem_package_old.rb b/test/rubygems/test_gem_package_old.rb
index ab7934dde5..d2ce59cfdd 100644
--- a/test/rubygems/test_gem_package_old.rb
+++ b/test/rubygems/test_gem_package_old.rb
@@ -1,89 +1,92 @@
 # frozen_string_literal: true
 require 'rubygems/test_case'
-require 'rubygems/simple_gem'
 
-class TestGemPackageOld < Gem::TestCase
+unless Gem.java_platform? # jruby can't require the simple_gem file
+  require 'rubygems/simple_gem'
 
-  def setup
-    super
+  class TestGemPackageOld < Gem::TestCase
 
-    File.open 'old_format.gem', 'wb' do |io|
-      io.write SIMPLE_GEM
-    end
+    def setup
+      super
 
-    @package = Gem::Package::Old.new 'old_format.gem'
-    @destination = File.join @tempdir, 'extract'
+      File.open 'old_format.gem', 'wb' do |io|
+        io.write SIMPLE_GEM
+      end
 
-    FileUtils.mkdir_p @destination
-  end
+      @package = Gem::Package::Old.new 'old_format.gem'
+      @destination = File.join @tempdir, 'extract'
 
-  def test_contents
-    assert_equal %w[lib/foo.rb lib/test.rb lib/test/wow.rb], @package.contents
-  end
+      FileUtils.mkdir_p @destination
+    end
 
-  def test_contents_security_policy
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    def test_contents
+      assert_equal %w[lib/foo.rb lib/test.rb lib/test/wow.rb], @package.contents
+    end
 
-    @package.security_policy = Gem::Security::AlmostNoSecurity
+    def test_contents_security_policy
+      skip 'openssl is missing' unless defined?(OpenSSL::SSL)
 
-    assert_raises Gem::Security::Exception do
-      @package.contents
+      @package.security_policy = Gem::Security::AlmostNoSecurity
+
+      assert_raises Gem::Security::Exception do
+        @package.contents
+      end
     end
-  end
 
-  def test_extract_files
-    @package.extract_files @destination
+    def test_extract_files
+      @package.extract_files @destination
 
-    extracted = File.join @destination, 'lib/foo.rb'
-    assert_path_exists extracted
+      extracted = File.join @destination, 'lib/foo.rb'
+      assert_path_exists extracted
 
-    mask = 0100644 & (~File.umask)
+      mask = 0100644 & (~File.umask)
 
-    assert_equal mask, File.stat(extracted).mode unless win_platform?
-  end
+      assert_equal mask, File.stat(extracted).mode unless win_platform?
+    end
 
-  def test_extract_files_security_policy
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    def test_extract_files_security_policy
+      skip 'openssl is missing' unless defined?(OpenSSL::SSL)
 
-    @package.security_policy = Gem::Security::AlmostNoSecurity
+      @package.security_policy = Gem::Security::AlmostNoSecurity
 
-    assert_raises Gem::Security::Exception do
-      @package.extract_files @destination
+      assert_raises Gem::Security::Exception do
+        @package.extract_files @destination
+      end
     end
-  end
 
-  def test_spec
-    assert_equal 'testing', @package.spec.name
-  end
+    def test_spec
+      assert_equal 'testing', @package.spec.name
+    end
 
-  def test_spec_security_policy
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    def test_spec_security_policy
+      skip 'openssl is missing' unless defined?(OpenSSL::SSL)
 
-    @package.security_policy = Gem::Security::AlmostNoSecurity
+      @package.security_policy = Gem::Security::AlmostNoSecurity
 
-    assert_raises Gem::Security::Exception do
-      @package.spec
+      assert_raises Gem::Security::Exception do
+        @package.spec
+      end
     end
-  end
 
-  def test_verify
-    skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    def test_verify
+      skip 'openssl is missing' unless defined?(OpenSSL::SSL)
 
-    assert @package.verify
+      assert @package.verify
 
-    @package.security_policy = Gem::Security::NoSecurity
+      @package.security_policy = Gem::Security::NoSecurity
 
-    assert @package.verify
+      assert @package.verify
 
-    @package.security_policy = Gem::Security::AlmostNoSecurity
+      @package.security_policy = Gem::Security::AlmostNoSecurity
 
-    e = assert_raises Gem::Security::Exception do
-      @package.verify
+      e = assert_raises Gem::Security::Exception do
+        @package.verify
+      end
+
+      assert_equal 'old format gems do not contain signatures ' +
+                   'and cannot be verified',
+                   e.message
     end
 
-    assert_equal 'old format gems do not contain signatures ' +
-                 'and cannot be verified',
-                 e.message
   end
-
 end
diff --git a/test/rubygems/test_gem_package_tar_header.rb b/test/rubygems/test_gem_package_tar_header.rb
index 5e804bb418..7e59073407 100644
--- a/test/rubygems/test_gem_package_tar_header.rb
+++ b/test/rubygems/test_gem_package_tar_header.rb
@@ -164,4 +164,45 @@ group\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000
     end
   end
 
+  def test_big_uid_gid
+    stream = StringIO.new(
+      <<-EOF.dup.force_encoding('binary').split("\n").join
+GeoIP2-City_20190528/
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x000000755\x00\x80\x00
+\x00\x00v\xB2Z\x9E\x80\x00\x00\x00v\xB2Z\x9E00000000000\x0013473270100\x00015424
+\x00 5\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00ustar  \x00
+tjmather\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00tjmather\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+\x00\x00\x00\x00
+      EOF
+    )
+
+    tar_header = Gem::Package::TarHeader.from stream
+
+    assert_equal 1991400094, tar_header.uid
+    assert_equal 1991400094, tar_header.gid
+
+    assert_equal 'GeoIP2-City_20190528/', tar_header.name
+    assert_equal 0755, tar_header.mode
+    assert_equal 0, tar_header.size
+    assert_equal 1559064640, tar_header.mtime
+    assert_equal 6932, tar_header.checksum
+  end
+
 end
diff --git a/test/rubygems/test_gem_package_tar_reader_entry.rb b/test/rubygems/test_gem_package_tar_reader_entry.rb
index 4627c230d9..87f3471678 100644
--- a/test/rubygems/test_gem_package_tar_reader_entry.rb
+++ b/test/rubygems/test_gem_package_tar_reader_entry.rb
@@ -76,6 +76,7 @@ class TestGemPackageTarReaderEntry < Gem::Package::TarTestCase
   end
 
   def test_full_name_null
+    skip "jruby strips the null byte and does not think it's corrupt" if Gem.java_platform?
     @entry.header.prefix << "\000"
 
     e = assert_raises Gem::Package::TarInvalidError do
diff --git a/test/rubygems/test_gem_path_support.rb b/test/rubygems/test_gem_path_support.rb
index 1f9cfe2c57..8715bb62dc 100644
--- a/test/rubygems/test_gem_path_support.rb
+++ b/test/rubygems/test_gem_path_support.rb
@@ -40,17 +40,19 @@ class TestGemPathSupport < Gem::TestCase
   end
 
   def test_initialize_path
-    ps = Gem::PathSupport.new ENV.to_hash.merge("GEM_PATH" => %W[#{@tempdir}/foo #{@tempdir}/bar].join(Gem.path_separator))
+    Gem.stub(:path_separator, File::PATH_SEPARATOR) do
+      ps = Gem::PathSupport.new ENV.to_hash.merge("GEM_PATH" => %W[#{@tempdir}/foo #{@tempdir}/bar].join(Gem.path_separator))
 
-    assert_equal ENV["GEM_HOME"], ps.home
+      assert_equal ENV["GEM_HOME"], ps.home
 
-    expected = [
-      File.join(@tempdir, 'foo'),
-      File.join(@tempdir, 'bar'),
-      ENV["GEM_HOME"],
-    ]
+      expected = [
+        File.join(@tempdir, 'foo'),
+        File.join(@tempdir, 'bar'),
+        ENV["GEM_HOME"],
+      ]
 
-    assert_equal expected, ps.path
+      assert_equal expected, ps.path
+    end
   end
 
   def test_initialize_regexp_path_separator
@@ -90,13 +92,15 @@ class TestGemPathSupport < Gem::TestCase
   end
 
   def test_initialize_home_path
-    ps = Gem::PathSupport.new("GEM_HOME" => "#{@tempdir}/foo",
-                              "GEM_PATH" => %W[#{@tempdir}/foo #{@tempdir}/bar].join(Gem.path_separator))
+    Gem.stub(:path_separator, File::PATH_SEPARATOR) do
+      ps = Gem::PathSupport.new("GEM_HOME" => "#{@tempdir}/foo",
+                                "GEM_PATH" => %W[#{@tempdir}/foo #{@tempdir}/bar].join(Gem.path_separator))
 
-    assert_equal File.join(@tempdir, "foo"), ps.home
+      assert_equal File.join(@tempdir, "foo"), ps.home
 
-    expected = [File.join(@tempdir, 'foo'), File.join(@tempdir, 'bar')]
-    assert_equal expected, ps.path
+      expected = [File.join(@tempdir, 'foo'), File.join(@tempdir, 'bar')]
+      assert_equal expected, ps.path
+    end
   end
 
   def util_path
diff --git a/test/rubygems/test_gem_remote_fetcher.rb b/test/rubygems/test_gem_remote_fetcher.rb
index e21ece2f50..7d5bcc23a9 100644
--- a/test/rubygems/test_gem_remote_fetcher.rb
+++ b/test/rubygems/test_gem_remote_fetcher.rb
@@ -785,6 +785,7 @@ PeIQQkFng2VVot/WAQbv3ePqWq07g1BBcwIBAg==
 
   def test_ssl_client_cert_auth_connection
     skip 'openssl is missing' unless defined?(OpenSSL::SSL)
+    skip 'openssl in jruby fails' if java_platform?
 
     ssl_server = self.class.start_ssl_server({
       :SSLVerifyClient =>
@@ -1050,12 +1051,4 @@ PeIQQkFng2VVot/WAQbv3ePqWq07g1BBcwIBAg==
 
   end
 
-  def test_correct_for_windows_path
-    path = "/C:/WINDOWS/Temp/gems"
-    assert_equal "C:/WINDOWS/Temp/gems", @fetcher.correct_for_windows_path(path)
-
-    path = "/home/skillet"
-    assert_equal "/home/skillet", @fetcher.correct_for_windows_path(path)
-  end
-
 end if defined?(OpenSSL::SSL)
diff --git a/test/rubygems/test_gem_request.rb b/test/rubygems/test_gem_request.rb
index 5f7d7bb7be..b9601b7c2c 100644
--- a/test/rubygems/test_gem_request.rb
+++ b/test/rubygems/test_gem_request.rb
@@ -328,6 +328,7 @@ class TestGemRequest < Gem::TestCase
   end
 
   def test_verify_certificate
+    skip if Gem.java_platform?
     store = OpenSSL::X509::Store.new
     context = OpenSSL::X509::StoreContext.new store
     context.error = OpenSSL::X509::V_ERR_OUT_OF_MEM
@@ -341,6 +342,7 @@ class TestGemRequest < Gem::TestCase
   end
 
   def test_verify_certificate_extra_message
+    skip if Gem.java_platform?
     store = OpenSSL::X509::Store.new
     context = OpenSSL::X509::StoreContext.new store
     context.error = OpenSSL::X509::V_ERR_INVALID_CA
diff --git a/test/rubygems/test_gem_request_set_gem_dependency_api.rb b/test/rubygems/test_gem_request_set_gem_dependency_api.rb
index 0df0bef215..24cfb67c4d 100644
--- a/test/rubygems/test_gem_request_set_gem_dependency_api.rb
+++ b/test/rubygems/test_gem_request_set_gem_dependency_api.rb
@@ -856,4 +856,4 @@ end
       engine
   end
 
-end
+end unless Gem.java_platform?
diff --git a/test/rubygems/test_gem_resolver.rb b/test/rubygems/test_gem_resolver.rb
index 4f88f83e16..172b46a33d 100644
--- a/test/rubygems/test_gem_resolver.rb
+++ b/test/rubygems/test_gem_resolver.rb
@@ -97,7 +97,7 @@ class TestGemResolver < Gem::TestCase
 
     r1 = Gem::Resolver::DependencyRequest.new dep('a', '= 1'), nil
 
-    act = Gem::Resolver::ActivationRequest.new a1, r1, false
+    act = Gem::Resolver::ActivationRequest.new a1, r1
 
     res = Gem::Resolver.new [a1]
 
@@ -118,7 +118,7 @@ class TestGemResolver < Gem::TestCase
 
     r1 = Gem::Resolver::DependencyRequest.new dep('a', '= 1'), nil
 
-    act = Gem::Resolver::ActivationRequest.new spec, r1, false
+    act = Gem::Resolver::ActivationRequest.new spec, r1
 
     res = Gem::Resolver.new [act]
     res.development = true
@@ -137,7 +137,7 @@ class TestGemResolver < Gem::TestCase
 
     r1 = Gem::Resolver::DependencyRequest.new dep('a', '= 1'), nil
 
-    act = Gem::Resolver::ActivationRequest.new a1, r1, false
+    act = Gem::Resolver::ActivationRequest.new a1, r1
 
     res = Gem::Resolver.new [a1]
     res.ignore_dependencies = true
diff --git a/test/rubygems/test_gem_resolver_activation_request.rb b/test/rubygems/test_gem_resolver_activation_request.rb
index 5d5de1a2d5..dc11ad47c4 100644
--- a/test/rubygems/test_gem_resolver_activation_request.rb
+++ b/test/rubygems/test_gem_resolver_activation_request.rb
@@ -13,11 +13,9 @@ class TestGemResolverActivationRequest < Gem::TestCase
     source   = Gem::Source::Local.new
     platform = Gem::Platform::RUBY
 
-    @a1 = @DR::IndexSpecification.new nil, 'a', v(1), source, platform
-    @a2 = @DR::IndexSpecification.new nil, 'a', v(2), source, platform
     @a3 = @DR::IndexSpecification.new nil, 'a', v(3), source, platform
 
-    @req = @DR::ActivationRequest.new @a3, @dep, [@a1, @a2]
+    @req = @DR::ActivationRequest.new @a3, @dep
   end
 
   def test_development_eh
@@ -25,7 +23,7 @@ class TestGemResolverActivationRequest < Gem::TestCase
 
     dep_req = @DR::DependencyRequest.new dep('a', '>= 0', :development), nil
 
-    act_req = @DR::ActivationRequest.new @a3, dep_req, [@a1, @a2]
+    act_req = @DR::ActivationRequest.new @a3, dep_req
 
     assert act_req.development?
   end
@@ -33,41 +31,14 @@ class TestGemResolverActivationRequest < Gem::TestCase
   def test_inspect
     assert_match 'a-3',                         @req.inspect
     assert_match 'from a (>= 0)',               @req.inspect
-    assert_match '(others possible: a-1, a-2)', @req.inspect
-  end
-
-  def test_inspect_legacy
-    req = @DR::ActivationRequest.new @a3, @dep, true
-
-    assert_match '(others possible)', req.inspect
-
-    req = @DR::ActivationRequest.new @a3, @dep, false
-
-    refute_match '(others possible)', req.inspect
   end
 
   def test_installed_eh
     v_spec = Gem::Resolver::VendorSpecification.new nil, @a3
 
-    @req = @DR::ActivationRequest.new v_spec, @dep, [@a1, @a2]
+    @req = @DR::ActivationRequest.new v_spec, @dep
 
     assert @req.installed?
   end
 
-  def test_others_possible_eh
-    assert @req.others_possible?
-
-    req = @DR::ActivationRequest.new @a3, @dep, []
-
-    refute req.others_possible?
-
-    req = @DR::ActivationRequest.new @a3, @dep, true
-
-    assert req.others_possible?
-
-    req = @DR::ActivationRequest.new @a3, @dep, false
-
-    refute req.others_possible?
-  end
-
 end
diff --git a/test/rubygems/test_gem_resolver_git_specification.rb b/test/rubygems/test_gem_resolver_git_specification.rb
index 3a9bb6a802..3391505555 100644
--- a/test/rubygems/test_gem_resolver_git_specification.rb
+++ b/test/rubygems/test_gem_resolver_git_specification.rb
@@ -63,6 +63,7 @@ class TestGemResolverGitSpecification < Gem::TestCase
   # functional test for Gem::Ext::Builder
 
   def test_install_extension
+    skip if Gem.java_platform?
     name, _, repository, = git_gem 'a', 1 do |s|
       s.extensions << 'ext/extconf.rb'
     end
diff --git a/test/rubygems/test_gem_security.rb b/test/rubygems/test_gem_security.rb
index 1ba3fa7d9c..71185dc86e 100644
--- a/test/rubygems/test_gem_security.rb
+++ b/test/rubygems/test_gem_security.rb
@@ -6,6 +6,10 @@ unless defined?(OpenSSL::SSL)
   warn 'Skipping Gem::Security tests.  openssl not found.'
 end
 
+if Gem.java_platform?
+  warn 'Skipping Gem::Security tests on jruby.'
+end
+
 class TestGemSecurity < Gem::TestCase
 
   CHILD_KEY = load_key 'child'
@@ -307,4 +311,4 @@ class TestGemSecurity < Gem::TestCase
     assert_equal key.to_pem, key_from_file.to_pem
   end
 
-end if defined?(OpenSSL::SSL)
+end if defined?(OpenSSL::SSL) && !Gem.java_platform?
diff --git a/test/rubygems/test_gem_security_signer.rb b/test/rubygems/test_gem_security_signer.rb
index 631afa87c4..08e74e6276 100644
--- a/test/rubygems/test_gem_security_signer.rb
+++ b/test/rubygems/test_gem_security_signer.rb
@@ -143,6 +143,7 @@ toqvglr0kdbknSRRjBVLK6tsgr07aLT9gNP7mTW2PA==
   end
 
   def test_sign_expired_auto_update
+    skip if Gem.java_platform?
     FileUtils.mkdir_p File.join(Gem.user_home, '.gem'), :mode => 0700
 
     private_key_path = File.join(Gem.user_home, '.gem', 'gem-private_key.pem')
diff --git a/test/rubygems/test_gem_source_git.rb b/test/rubygems/test_gem_source_git.rb
index 2dafcacc8e..22fbdee05e 100644
--- a/test/rubygems/test_gem_source_git.rb
+++ b/test/rubygems/test_gem_source_git.rb
@@ -236,11 +236,6 @@ class TestGemSourceGit < Gem::TestCase
         system @git, 'add', 'b.gemspec'
         system @git, 'commit', '--quiet', '-m', 'add b/b.gemspec'
       end
-
-      FileUtils.touch 'c.gemspec'
-
-      system @git, 'add', 'c.gemspec'
-      system @git, 'commit', '--quiet', '-m', 'add c.gemspec'
     end
 
     specs = nil
diff --git a/test/rubygems/test_gem_specification.rb b/test/rubygems/test_gem_specification.rb
index 5024cfbc52..4d3fb93ff1 100644
--- a/test/rubygems/test_gem_specification.rb
+++ b/test/rubygems/test_gem_specification.rb
@@ -1441,6 +1441,7 @@ dependencies: []
   end
 
   def test_build_args
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     assert_empty @ext.build_args
@@ -1459,6 +1460,7 @@ dependencies: []
   end
 
   def test_build_extensions
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_path_exists @ext.extension_dir, 'sanity check'
@@ -1494,6 +1496,7 @@ dependencies: []
   end
 
   def test_build_extensions_built
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_empty @ext.extensions, 'sanity check'
@@ -1532,6 +1535,7 @@ dependencies: []
   end
 
   def test_build_extensions_error
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_empty @ext.extensions, 'sanity check'
@@ -1545,6 +1549,7 @@ dependencies: []
     skip 'chmod not supported' if Gem.win_platform?
     skip 'skipped in root privilege' if Process.uid.zero?
 
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_empty @ext.extensions, 'sanity check'
@@ -1569,7 +1574,7 @@ dependencies: []
     @ext.build_extensions
     refute_path_exists @ext.extension_dir
   ensure
-    unless ($DEBUG or win_platform? or Process.uid.zero?)
+    unless ($DEBUG or win_platform? or Process.uid.zero? or Gem.java_platform?)
       FileUtils.chmod 0755, File.join(@ext.base_dir, 'extensions')
       FileUtils.chmod 0755, @ext.base_dir
     end
@@ -1577,7 +1582,7 @@ dependencies: []
 
   def test_build_extensions_no_extensions_dir_unwritable
     skip 'chmod not supported' if Gem.win_platform?
-
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_empty @ext.extensions, 'sanity check'
@@ -1616,6 +1621,7 @@ dependencies: []
   end
 
   def test_build_extensions_old
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     refute_empty @ext.extensions, 'sanity check'
@@ -1629,6 +1635,7 @@ dependencies: []
   end
 
   def test_build_extensions_preview
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     extconf_rb = File.join @ext.gem_dir, @ext.extensions.first
@@ -1663,6 +1670,7 @@ dependencies: []
   end
 
   def test_contains_requirable_file_eh_extension
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     _, err = capture_io do
@@ -3623,6 +3631,7 @@ end
   end
 
   def test_missing_extensions_eh
+    skip "extensions don't quite work on jruby" if Gem.java_platform?
     ext_spec
 
     assert @ext.missing_extensions?
diff --git a/test/rubygems/test_gem_stub_specification.rb b/test/rubygems/test_gem_stub_specification.rb
index 10f8c04a0e..8553194c44 100644
--- a/test/rubygems/test_gem_stub_specification.rb
+++ b/test/rubygems/test_gem_stub_specification.rb
@@ -67,6 +67,7 @@ class TestStubSpecification < Gem::TestCase
   end
 
   def test_contains_requirable_file_eh_extension
+    skip "I guess making the stub match the running platform should work" if Gem.java_platform?
     stub_with_extension do |stub|
       _, err = capture_io do
         refute stub.contains_requirable_file? 'nonexistent'
@@ -123,6 +124,7 @@ class TestStubSpecification < Gem::TestCase
   end
 
   def test_missing_extensions_eh
+    skip "I guess making the stub match the running platform should work" if Gem.java_platform?
     stub = stub_with_extension do |s|
       extconf_rb = File.join s.gem_dir, s.extensions.first
       FileUtils.mkdir_p File.dirname extconf_rb
diff --git a/test/rubygems/test_gem_uninstaller.rb b/test/rubygems/test_gem_uninstaller.rb
index 7440ca0191..9dfef7cfda 100644
--- a/test/rubygems/test_gem_uninstaller.rb
+++ b/test/rubygems/test_gem_uninstaller.rb
@@ -6,6 +6,8 @@ class TestGemUninstaller < Gem::InstallerTestCase
 
   def setup
     super
+    @installer = setup_base_installer
+    @user_installer = setup_base_user_installer
     common_installer_setup
 
     build_rake_in do
diff --git a/test/rubygems/test_gem_util.rb b/test/rubygems/test_gem_util.rb
index a48d275d28..3f1d069a20 100644
--- a/test/rubygems/test_gem_util.rb
+++ b/test/rubygems/test_gem_util.rb
@@ -5,6 +5,7 @@ require 'rubygems/util'
 class TestGemUtil < Gem::TestCase
 
   def test_class_popen
+    skip "popen with a block does not behave well on jruby" if Gem.java_platform?
     assert_equal "0\n", Gem::Util.popen(Gem.ruby, '-I', File.expand_path('../../../lib', __FILE__), '-e', 'p 0')
 
     assert_raises Errno::ECHILD do
@@ -13,6 +14,7 @@ class TestGemUtil < Gem::TestCase
   end
 
   def test_silent_system
+    skip if Gem.java_platform?
     assert_silent do
       Gem::Util.silent_system Gem.ruby, '-I', File.expand_path('../../../lib', __FILE__), '-e', 'puts "hello"; warn "hello"'
     end
@@ -30,7 +32,7 @@ class TestGemUtil < Gem::TestCase
   end
 
   def test_traverse_parents_does_not_crash_on_permissions_error
-    skip 'skipped on MS Windows (chmod has no effect)' if win_platform?
+    skip 'skipped on MS Windows (chmod has no effect)' if win_platform? || java_platform?
 
     FileUtils.mkdir_p 'd/e/f'
     # remove 'execute' permission from "e" directory and make it
@@ -47,7 +49,7 @@ class TestGemUtil < Gem::TestCase
     assert_equal File.realpath("..", Dir.tmpdir), paths[3]
   ensure
     # restore default permissions, allow the directory to be removed
-    FileUtils.chmod(0775, 'd/e') unless win_platform?
+    FileUtils.chmod(0775, 'd/e') unless win_platform? || java_platform?
   end
 
   def test_linked_list_find
@@ -75,4 +77,12 @@ class TestGemUtil < Gem::TestCase
     assert_equal expected_paths.to_set, files_with_relative_base.to_set
   end
 
+  def test_correct_for_windows_path
+    path = "/C:/WINDOWS/Temp/gems"
+    assert_equal "C:/WINDOWS/Temp/gems", Gem::Util.correct_for_windows_path(path)
+
+    path = "/home/skillet"
+    assert_equal "/home/skillet", Gem::Util.correct_for_windows_path(path)
+  end
+
 end
diff --git a/test/rubygems/test_gem_validator.rb b/test/rubygems/test_gem_validator.rb
index b9f597b7d3..34b7e5fb37 100644
--- a/test/rubygems/test_gem_validator.rb
+++ b/test/rubygems/test_gem_validator.rb
@@ -1,14 +1,13 @@
 # frozen_string_literal: true
-require 'rubygems/test_case'
-require "rubygems/simple_gem"
-require 'rubygems/validator'
+
+require "rubygems/test_case"
+require "rubygems/validator"
 
 class TestGemValidator < Gem::TestCase
 
   def setup
     super
 
-    @simple_gem = SIMPLE_GEM
     @validator = Gem::Validator.new
   end
 
diff --git a/test/rubygems/test_require.rb b/test/rubygems/test_require.rb
index 678dde2cae..7c86748a87 100644
--- a/test/rubygems/test_require.rb
+++ b/test/rubygems/test_require.rb
@@ -162,6 +162,10 @@ class TestGemRequire < Gem::TestCase
   end
 
   def test_activate_via_require_respects_loaded_files
+    skip "Not sure what's going on. If another spec creates a 'a' gem before
+      this test, somehow require will load the benchmark in b, and ignore that the
+      stdlib one is already in $LOADED_FEATURES?. Reproducible by running the
+      spaceship_specific_file test before this one" if java_platform?
     a1 = util_spec "a", "1", {"b" => ">= 1"}, "lib/test_gem_require_a.rb"
     b1 = util_spec "b", "1", nil, "lib/benchmark.rb"
     b2 = util_spec "b", "2", nil, "lib/benchmark.rb"
@@ -431,7 +435,8 @@ class TestGemRequire < Gem::TestCase
     end
   end
 
-  if RUBY_VERSION >= "2.5"
+  # uplevel is 2.5+ only and jruby has some issues with it
+  if RUBY_VERSION >= "2.5" && !java_platform?
     def test_no_kernel_require_in_warn_with_uplevel
       lib = File.realpath("../../../lib", __FILE__)
       Dir.mktmpdir("warn_test") do |dir|