diff --git a/spec/ruby/.rubocop.yml b/spec/ruby/.rubocop.yml
index fff542a222..762fe42bad 100644
--- a/spec/ruby/.rubocop.yml
+++ b/spec/ruby/.rubocop.yml
@@ -32,9 +32,6 @@ Lint/LiteralAsCondition:
 Lint/UnneededRequireStatement:
   Enabled: false
 
-Lint/RescueWithoutErrorClass:
-  Enabled: false
-
 Lint/UnifiedInteger:
   Enabled: false
 
diff --git a/spec/ruby/.rubocop_todo.yml b/spec/ruby/.rubocop_todo.yml
index 05ce1e9af8..c227ca032d 100644
--- a/spec/ruby/.rubocop_todo.yml
+++ b/spec/ruby/.rubocop_todo.yml
@@ -1,18 +1,11 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2017-10-09 20:22:01 +0200 using RuboCop version 0.50.0.
+# on 2017-12-15 22:14:22 +0900 using RuboCop version 0.52.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 3
-Lint/CircularArgumentReference:
-  Exclude:
-    - 'language/block_spec.rb'
-    - 'language/def_spec.rb'
-    - 'language/lambda_spec.rb'
-
 # Offense count: 2
 Lint/DuplicateCaseCondition:
   Exclude:
@@ -44,15 +37,13 @@ Lint/FloatOutOfRange:
   Exclude:
     - 'core/string/modulo_spec.rb'
 
-# Offense count: 43
+# Offense count: 107
 Lint/FormatParameterMismatch:
   Exclude:
-    - 'core/kernel/sprintf_spec.rb'
-    - 'core/string/modulo_spec.rb'
     - 'core/kernel/shared/sprintf.rb'
-    - 'core/kernel/shared/sprintf_encoding.rb'
+    - 'core/string/modulo_spec.rb'
 
-# Offense count: 25
+# Offense count: 28
 Lint/HandleExceptions:
   Enabled: false
 
@@ -70,7 +61,7 @@ Lint/IneffectiveAccessModifier:
 
 # Offense count: 5
 # Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, SupportedStyles.
+# Configuration parameters: EnforcedStyle.
 # SupportedStyles: runtime_error, standard_error
 Lint/InheritException:
   Exclude:
@@ -84,6 +75,7 @@ Lint/LiteralInInterpolation:
   Exclude:
     - 'language/defined_spec.rb'
     - 'language/fixtures/squiggly_heredoc.rb'
+    - 'core/module/refine_spec.rb'
 
 # Offense count: 16
 Lint/Loop:
@@ -112,7 +104,13 @@ Lint/ParenthesesAsGroupedExpression:
     - 'language/method_spec.rb'
     - 'library/socket/socket/getaddrinfo_spec.rb'
 
-# Offense count: 22
+# Offense count: 1
+# Cop supports --auto-correct.
+Lint/RedundantWithIndex:
+  Exclude:
+    - 'core/enumerator/with_index_spec.rb'
+
+# Offense count: 24
 Lint/RescueException:
   Exclude:
     - 'command_line/fixtures/debug_info.rb'
@@ -136,6 +134,12 @@ Lint/ScriptPermission:
   Exclude:
     - 'command_line/fixtures/bin/launcher.rb'
 
+# Offense count: 2
+# Configuration parameters: IgnoreImplicitReferences.
+Lint/ShadowedArgument:
+  Exclude:
+    - 'language/fixtures/super.rb'
+
 # Offense count: 10
 Lint/ShadowingOuterLocalVariable:
   Exclude:
@@ -156,12 +160,11 @@ Lint/UnderscorePrefixedVariableName:
     - 'core/io/popen_spec.rb'
     - 'language/block_spec.rb'
 
-# Offense count: 91
+# Offense count: 90
 # Cop supports --auto-correct.
 Lint/UnneededSplatExpansion:
   Exclude:
     - 'core/array/element_reference_spec.rb'
-    - 'core/array/unshift_spec.rb'
     - 'core/enumerable/fixtures/classes.rb'
     - 'core/enumerable/max_by_spec.rb'
     - 'core/enumerable/min_by_spec.rb'
@@ -176,7 +179,7 @@ Lint/UnneededSplatExpansion:
     - 'language/send_spec.rb'
     - 'language/variables_spec.rb'
 
-# Offense count: 55
+# Offense count: 54
 Lint/UnreachableCode:
   Exclude:
     - 'core/enumerator/lazy/fixtures/classes.rb'
diff --git a/spec/ruby/.travis.yml b/spec/ruby/.travis.yml
index e8a9106ac1..767d437f67 100644
--- a/spec/ruby/.travis.yml
+++ b/spec/ruby/.travis.yml
@@ -3,7 +3,7 @@ language: ruby
 install:
   - git clone https://github.com/ruby/mspec.git ../mspec
 script:
-  - if [ -n "$RUBOCOP" ]; then gem install rubocop -v 0.51.0 && rubocop; fi
+  - if [ -n "$RUBOCOP" ]; then gem install rubocop -v 0.52.0 && rubocop; fi
   - ../mspec/bin/mspec $MSPEC_OPTS
 matrix:
   include:
diff --git a/spec/ruby/README.md b/spec/ruby/README.md
index 970688a623..9c13ede75c 100644
--- a/spec/ruby/README.md
+++ b/spec/ruby/README.md
@@ -2,6 +2,7 @@
 
 [![Build Status](https://travis-ci.org/ruby/spec.svg)](https://travis-ci.org/ruby/spec)
 [![Build Status](https://ci.appveyor.com/api/projects/status/1gs6f399320o44b1?svg=true)](https://ci.appveyor.com/project/eregon/spec-x948i)
+[![Gitter](https://badges.gitter.im/ruby/spec.svg)](https://gitter.im/ruby/spec)
 
 The Ruby Spec Suite is a test suite for the behavior of the Ruby programming language.
 
diff --git a/spec/ruby/core/dir/children_spec.rb b/spec/ruby/core/dir/children_spec.rb
new file mode 100644
index 0000000000..a80e685996
--- /dev/null
+++ b/spec/ruby/core/dir/children_spec.rb
@@ -0,0 +1,72 @@
+# encoding: utf-8
+
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/common', __FILE__)
+
+ruby_version_is "2.5" do
+  describe "Dir.children" do
+    before :all do
+      DirSpecs.create_mock_dirs
+    end
+
+    before :each do
+      @internal = Encoding.default_internal
+    end
+
+    after :all do
+      DirSpecs.delete_mock_dirs
+    end
+
+    after :each do
+      Encoding.default_internal = @internal
+    end
+
+    it "returns an Array of filenames in an existing directory including dotfiles" do
+      a = Dir.children(DirSpecs.mock_dir).sort
+
+      a.should == DirSpecs.expected_paths - %w[. ..]
+
+      a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested").sort
+      a.should == %w|.dotfile.ext directory|
+    end
+
+    it "calls #to_path on non-String arguments" do
+      p = mock('path')
+      p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
+      Dir.children(p)
+    end
+
+    it "accepts an options Hash" do
+      a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").sort
+      a.should == %w|.dotfile.ext directory|
+    end
+
+    it "returns children encoded with the filesystem encoding by default" do
+      # This spec depends on the locale not being US-ASCII because if it is, the
+      # children that are not ascii_only? will be ASCII-8BIT encoded.
+      children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
+      encoding = Encoding.find("filesystem")
+      encoding = Encoding::ASCII_8BIT if encoding == Encoding::US_ASCII
+      platform_is_not :windows do
+        children.should include("こんにちは.txt".force_encoding(encoding))
+      end
+      children.first.encoding.should equal(Encoding.find("filesystem"))
+    end
+
+    it "returns children encoded with the specified encoding" do
+      dir = File.join(DirSpecs.mock_dir, 'special')
+      children = Dir.children(dir, encoding: "euc-jp").sort
+      children.first.encoding.should equal(Encoding::EUC_JP)
+    end
+
+    it "returns children transcoded to the default internal encoding" do
+      Encoding.default_internal = Encoding::EUC_KR
+      children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
+      children.first.encoding.should equal(Encoding::EUC_KR)
+    end
+
+    it "raises a SystemCallError if called with a nonexistent diretory" do
+      lambda { Dir.children DirSpecs.nonexistent }.should raise_error(SystemCallError)
+    end
+  end
+end
diff --git a/spec/ruby/core/dir/each_child_spec.rb b/spec/ruby/core/dir/each_child_spec.rb
new file mode 100644
index 0000000000..70f6f63333
--- /dev/null
+++ b/spec/ruby/core/dir/each_child_spec.rb
@@ -0,0 +1,53 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/common', __FILE__)
+
+ruby_version_is "2.5" do
+  describe "Dir.each_child" do
+    before :all do
+      DirSpecs.create_mock_dirs
+    end
+
+    after :all do
+      DirSpecs.delete_mock_dirs
+    end
+
+    it "yields all names in an existing directory to the provided block" do
+      a, b = [], []
+
+      Dir.each_child(DirSpecs.mock_dir) {|f| a << f}
+      Dir.each_child("#{DirSpecs.mock_dir}/deeply/nested") {|f| b << f}
+
+      a.sort.should == DirSpecs.expected_paths -  %w[. ..]
+      b.sort.should == %w|.dotfile.ext directory|
+    end
+
+    it "returns nil when successful" do
+      Dir.each_child(DirSpecs.mock_dir) {|f| f}.should == nil
+    end
+
+    it "calls #to_path on non-String arguments" do
+      p = mock('path')
+      p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
+      Dir.each_child(p).to_a
+    end
+
+    it "raises a SystemCallError if passed a nonexistent directory" do
+      lambda { Dir.each_child(DirSpecs.nonexistent) {} }.should raise_error(SystemCallError)
+    end
+
+    describe "when no block is given" do
+      it "returns an Enumerator" do
+        Dir.each_child(DirSpecs.mock_dir).should be_an_instance_of(Enumerator)
+        Dir.each_child(DirSpecs.mock_dir).to_a.sort.should == DirSpecs.expected_paths - %w[. ..]
+      end
+
+      describe "returned Enumerator" do
+        describe "size" do
+          it "should return nil" do
+            Dir.each_child(DirSpecs.mock_dir).size.should == nil
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/encoding/locale_charmap_spec.rb b/spec/ruby/core/encoding/locale_charmap_spec.rb
index 12b93c2562..a9f0cd5ee0 100644
--- a/spec/ruby/core/encoding/locale_charmap_spec.rb
+++ b/spec/ruby/core/encoding/locale_charmap_spec.rb
@@ -16,7 +16,7 @@ with_feature :encoding do
       end
     end
 
-    platform_is :freebsd, :darwin do
+    platform_is :freebsd, :openbsd, :darwin do
       it "returns a value based on the LC_ALL environment variable" do
         old_lc_all = ENV['LC_ALL']
         ENV['LC_ALL'] = 'C'
@@ -25,7 +25,7 @@ with_feature :encoding do
       end
     end
 
-    platform_is :netbsd, :openbsd do
+    platform_is :netbsd do
       it "returns a value based on the LC_ALL environment variable" do
         old_lc_all = ENV['LC_ALL']
         ENV['LC_ALL'] = 'C'
diff --git a/spec/ruby/core/enumerable/all_spec.rb b/spec/ruby/core/enumerable/all_spec.rb
index bfde584260..9e40315baa 100644
--- a/spec/ruby/core/enumerable/all_spec.rb
+++ b/spec/ruby/core/enumerable/all_spec.rb
@@ -54,10 +54,20 @@ describe "Enumerable#all?" do
     end
 
     it "gathers whole arrays as elements when each yields multiple" do
+      # This spec doesn't spec what it says it does
       multi = EnumerableSpecs::YieldsMultiWithFalse.new
       multi.all?.should be_true
     end
 
+    ruby_version_is "2.5" do
+      describe "given a pattern argument" do
+        # This spec should be replaced by more extensive ones
+        it "returns true iff all match that pattern" do
+          @enum.all?(Integer).should == true
+          @enum2.all?(NilClass).should == false
+        end
+      end
+    end
   end
 
   describe "with block" do
@@ -116,6 +126,5 @@ describe "Enumerable#all?" do
       multi.all? {|e, i| yielded << [e, i] }
       yielded.should == [[1, 2], [3, 4], [6, 7]]
     end
-
   end
 end
diff --git a/spec/ruby/core/enumerable/none_spec.rb b/spec/ruby/core/enumerable/none_spec.rb
index 0646c13b34..89472d6ee1 100644
--- a/spec/ruby/core/enumerable/none_spec.rb
+++ b/spec/ruby/core/enumerable/none_spec.rb
@@ -13,9 +13,20 @@ describe "Enumerable#none?" do
   end
 
   it "gathers whole arrays as elements when each yields multiple" do
+    # This spec doesn't spec what it says it does
     multi = EnumerableSpecs::YieldsMultiWithFalse.new
     multi.none?.should be_false
   end
+
+  ruby_version_is "2.5" do
+    describe "given a pattern argument" do
+      # This spec should be replaced by more extensive ones
+      it "returns true iff none match that pattern" do
+        EnumerableSpecs::Numerous.new.none?(Float).should == true
+        [nil, false, true].none?(NilClass).should == false
+      end
+    end
+  end
 end
 
 describe "Enumerable#none? with a block" do
diff --git a/spec/ruby/core/enumerable/one_spec.rb b/spec/ruby/core/enumerable/one_spec.rb
index 818d4663a4..5f118e3323 100644
--- a/spec/ruby/core/enumerable/one_spec.rb
+++ b/spec/ruby/core/enumerable/one_spec.rb
@@ -16,6 +16,7 @@ describe "Enumerable#one?" do
     end
 
     it "gathers initial args as elements when each yields multiple" do
+      # This spec doesn't spec what it says it does
       multi = EnumerableSpecs::YieldsMulti.new
       multi.one? {|e| e == 1 }.should be_true
     end
@@ -26,6 +27,16 @@ describe "Enumerable#one?" do
       multi.one? {|e, i| yielded << [e, i] }
       yielded.should == [[1, 2], [3, 4]]
     end
+
+    ruby_version_is "2.5" do
+      describe "given a pattern argument" do
+        # This spec should be replaced by more extensive ones
+        it "returns true iff none match that pattern" do
+          EnumerableSpecs::Numerous.new.one?(Integer).should == false
+          [nil, false, true].one?(NilClass).should == true
+        end
+      end
+    end
   end
 
   describe "when not passed a block" do
diff --git a/spec/ruby/core/file/chown_spec.rb b/spec/ruby/core/file/chown_spec.rb
index a0b46e9e39..6266e12bfd 100644
--- a/spec/ruby/core/file/chown_spec.rb
+++ b/spec/ruby/core/file/chown_spec.rb
@@ -91,17 +91,17 @@ describe "File#chown" do
   as_superuser do
     platform_is :windows do
       it "does not modify the owner id of the file" do
-        File.chown 0, nil, @fname
-        File.stat(@fname).uid.should == 0
-        File.chown 501, nil, @fname
-        File.stat(@fname).uid.should == 0
+        @file.chown 0, nil
+        @file.stat.uid.should == 0
+        @file.chown 501, nil
+        @file.stat.uid.should == 0
       end
 
       it "does not modify the group id of the file" do
-        File.chown nil, 0, @fname
-        File.stat(@fname).gid.should == 0
-        File.chown nil, 501, @fname
-        File.stat(@fname).gid.should == 0
+        @file.chown nil, 0
+        @file.stat.gid.should == 0
+        @file.chown nil, 501
+        @file.stat.gid.should == 0
       end
     end
 
diff --git a/spec/ruby/core/file/shared/read.rb b/spec/ruby/core/file/shared/read.rb
index 916a6222bf..e37523c244 100644
--- a/spec/ruby/core/file/shared/read.rb
+++ b/spec/ruby/core/file/shared/read.rb
@@ -1,13 +1,13 @@
 require File.expand_path('../../../dir/fixtures/common', __FILE__)
 
 describe :file_read_directory, shared: true do
-  platform_is :darwin, :linux, :windows do
+  platform_is :darwin, :linux, :openbsd, :windows do
     it "raises an Errno::EISDIR when passed a path that is a directory" do
       lambda { @object.send(@method, ".") }.should raise_error(Errno::EISDIR)
     end
   end
 
-  platform_is :bsd do
+  platform_is :freebsd, :netbsd do
     it "does not raises any exception when passed a path that is a directory" do
       lambda { @object.send(@method, ".") }.should_not raise_error
     end
diff --git a/spec/ruby/core/file/stat/inspect_spec.rb b/spec/ruby/core/file/stat/inspect_spec.rb
index dd2ad21da3..ec99ab16a8 100644
--- a/spec/ruby/core/file/stat/inspect_spec.rb
+++ b/spec/ruby/core/file/stat/inspect_spec.rb
@@ -16,7 +16,7 @@ describe "File::Stat#inspect" do
     expected = "#<File::Stat dev=0x#{st.dev.to_s(16)}, ino=#{st.ino}, mode=#{sprintf("%07o", st.mode)}, nlink=#{st.nlink}"
     expected << ", uid=#{st.uid}, gid=#{st.gid}, rdev=0x#{st.rdev.to_s(16)}, size=#{st.size}, blksize=#{st.blksize.inspect}"
     expected << ", blocks=#{st.blocks.inspect}, atime=#{st.atime}, mtime=#{st.mtime}, ctime=#{st.ctime}"
-    platform_is :bsd, :darwin do
+    platform_is :netbsd, :freebsd, :darwin do
       # Windows has File.birthtime but it's not here since already shown by ctime.
       expected << ", birthtime=#{st.birthtime}"
     end
diff --git a/spec/ruby/core/hash/slice_spec.rb b/spec/ruby/core/hash/slice_spec.rb
new file mode 100644
index 0000000000..15c9c815ff
--- /dev/null
+++ b/spec/ruby/core/hash/slice_spec.rb
@@ -0,0 +1,36 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+ruby_version_is "2.5" do
+  describe "Hash#slice" do
+    before :each do
+      @hash = { a: 1, b: 2, c: 3 }
+    end
+
+    it "returns new hash" do
+      ret = @hash.slice
+      ret.should_not equal(@hash)
+      ret.should be_an_instance_of(Hash)
+    end
+
+    it "returns the requested subset" do
+      @hash.slice(:c, :a).should == { c: 3, a: 1 }
+    end
+
+    it "returns a hash ordered in the order of the requested keys" do
+      @hash.slice(:c, :a).keys.should == [:c, :a]
+    end
+
+    it "returns only the keys of the original hash" do
+      @hash.slice(:a, :chunky_bacon).should == { a: 1 }
+    end
+
+    it "returns a Hash instance, even on subclasses" do
+      klass = Class.new(Hash)
+      h = klass.new
+      h[:foo] = 42
+      r = h.slice(:foo)
+      r.should == {foo: 42}
+      r.class.should == Hash
+    end
+  end
+end
diff --git a/spec/ruby/core/hash/transform_keys_spec.rb b/spec/ruby/core/hash/transform_keys_spec.rb
new file mode 100644
index 0000000000..379638bd4b
--- /dev/null
+++ b/spec/ruby/core/hash/transform_keys_spec.rb
@@ -0,0 +1,110 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+ruby_version_is "2.5" do
+  describe "Hash#transform_keys" do
+    before :each do
+      @hash = { a: 1, b: 2, c: 3 }
+    end
+
+    it "returns new hash" do
+      ret = @hash.transform_keys(&:succ)
+      ret.should_not equal(@hash)
+      ret.should be_an_instance_of(Hash)
+    end
+
+    it "sets the result as transformed keys with the given block" do
+      @hash.transform_keys(&:succ).should ==  { b: 1, c: 2, d: 3 }
+    end
+
+    it "keeps last pair if new keys conflict" do
+      @hash.transform_keys { |_| :a }.should == { a: 3 }
+    end
+
+    it "makes both hashes to share values" do
+      value = [1, 2, 3]
+      new_hash = { a: value }.transform_keys(&:upcase)
+      new_hash[:A].should equal(value)
+    end
+
+    context "when no block is given" do
+      it "returns a sized Enumerator" do
+        enumerator = @hash.transform_keys
+        enumerator.should be_an_instance_of(Enumerator)
+        enumerator.size.should == @hash.size
+        enumerator.each(&:succ).should == { b: 1, c: 2, d: 3 }
+      end
+    end
+
+    it "returns a Hash instance, even on subclasses" do
+      klass = Class.new(Hash)
+      h = klass.new
+      h[:foo] = 42
+      r = h.transform_keys{|v| :"x#{v}"}
+      r.keys.should == [:xfoo]
+      r.class.should == Hash
+    end
+  end
+
+  describe "Hash#transform_keys!" do
+    before :each do
+      @hash = { a: 1, b: 2, c: 3, d: 4 }
+      @initial_pairs = @hash.dup
+    end
+
+    it "returns self" do
+      @hash.transform_keys!(&:succ).should equal(@hash)
+    end
+
+    it "updates self as transformed values with the given block" do
+      @hash.transform_keys!(&:to_s)
+      @hash.should == { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4 }
+    end
+
+    it "does not prevent conflicts between new keys and old ones" do
+      @hash.transform_keys!(&:succ)
+      @hash.should == { e: 1 }
+    end
+
+    it "partially modifies the contents if we broke from the block" do
+      @hash.transform_keys! do |v|
+        break if v == :c
+        v.succ
+      end
+      @hash.should == { c: 1, d: 4 }
+    end
+
+    it "keeps later pair if new keys conflict" do
+      @hash.transform_keys! { |_| :a }.should == { a: 4 }
+    end
+
+    context "when no block is given" do
+      it "returns a sized Enumerator" do
+        enumerator = @hash.transform_keys!
+        enumerator.should be_an_instance_of(Enumerator)
+        enumerator.size.should == @hash.size
+        enumerator.each(&:upcase).should == { A: 1, B: 2, C: 3, D: 4 }
+      end
+    end
+
+    describe "on frozen instance" do
+      before :each do
+        @hash.freeze
+      end
+
+      it "raises a RuntimeError on an empty hash" do
+        ->{ {}.freeze.transform_keys!(&:upcase) }.should raise_error(RuntimeError)
+      end
+
+      it "keeps pairs and raises a RuntimeError" do
+        ->{ @hash.transform_keys!(&:upcase) }.should raise_error(RuntimeError)
+        @hash.should == @initial_pairs
+      end
+
+      context "when no block is given" do
+        it "does not raise an exception" do
+          @hash.transform_keys!.should be_an_instance_of(Enumerator)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/hash/transform_values_spec.rb b/spec/ruby/core/hash/transform_values_spec.rb
index 0c9e43d621..a9098a9f2d 100644
--- a/spec/ruby/core/hash/transform_values_spec.rb
+++ b/spec/ruby/core/hash/transform_values_spec.rb
@@ -16,6 +16,13 @@ ruby_version_is "2.4" do
       @hash.transform_values(&:succ).should ==  { a: 2, b: 3, c: 4 }
     end
 
+    it "makes both hashes to share keys" do
+      key = [1, 2, 3]
+      new_hash = { key => 1 }.transform_values(&:succ)
+      new_hash[key].should == 2
+      new_hash.keys[0].should equal(key)
+    end
+
     context "when no block is given" do
       it "returns a sized Enumerator" do
         enumerator = @hash.transform_values
@@ -47,7 +54,7 @@ ruby_version_is "2.4" do
 
     it "updates self as transformed values with the given block" do
       @hash.transform_values!(&:succ)
-      @hash.should ==  { a: 2, b: 3, c: 4 }
+      @hash.should == { a: 2, b: 3, c: 4 }
     end
 
     it "partially modifies the contents if we broke from the block" do
diff --git a/spec/ruby/core/kernel/autoload_spec.rb b/spec/ruby/core/kernel/autoload_spec.rb
index b9715eea66..b2aab5a895 100644
--- a/spec/ruby/core/kernel/autoload_spec.rb
+++ b/spec/ruby/core/kernel/autoload_spec.rb
@@ -57,7 +57,7 @@ describe "Kernel#autoload" do
 
   describe "when Object is frozen" do
     it "raises a FrozenError before defining the constant" do
-      ruby_exe(fixture(__FILE__, "autoload_frozen.rb")).should == "FrozenError - nil"
+      ruby_exe(fixture(__FILE__, "autoload_frozen.rb")).should == "#{frozen_error_class} - nil"
     end
   end
 end
diff --git a/spec/ruby/core/module/included_modules_spec.rb b/spec/ruby/core/module/included_modules_spec.rb
index 91e1298eef..ff2dc434dd 100644
--- a/spec/ruby/core/module/included_modules_spec.rb
+++ b/spec/ruby/core/module/included_modules_spec.rb
@@ -4,9 +4,9 @@ require File.expand_path('../fixtures/classes', __FILE__)
 describe "Module#included_modules" do
   it "returns a list of modules included in self" do
     ModuleSpecs.included_modules.should == []
-    ModuleSpecs::Child.included_modules.should  include(ModuleSpecs::Super, ModuleSpecs::Basic, Kernel)
+    ModuleSpecs::Child.included_modules.should include(ModuleSpecs::Super, ModuleSpecs::Basic, Kernel)
     ModuleSpecs::Parent.included_modules.should include(Kernel)
     ModuleSpecs::Basic.included_modules.should == []
-    ModuleSpecs::Super.included_modules.should  include(ModuleSpecs::Basic)
+    ModuleSpecs::Super.included_modules.should include(ModuleSpecs::Basic)
   end
 end
diff --git a/spec/ruby/core/module/refine_spec.rb b/spec/ruby/core/module/refine_spec.rb
index b54d83075f..ca7db0c2b6 100644
--- a/spec/ruby/core/module/refine_spec.rb
+++ b/spec/ruby/core/module/refine_spec.rb
@@ -320,7 +320,7 @@ describe "Module#refine" do
     result.should == "foo from subclass"
   end
 
-  context "for methods accesses indirectly" do
+  context "for methods accessed indirectly" do
     ruby_version_is "" ... "2.4" do
       it "is not honored by Kernel#send" do
         refinement = Module.new do
@@ -425,6 +425,46 @@ describe "Module#refine" do
       end
     end
 
+    ruby_version_is "" ... "2.5" do
+      it "is not honored by string interpolation" do
+        refinement = Module.new do
+          refine Integer do
+            def to_s
+              "foo"
+            end
+          end
+        end
+
+        result = nil
+        Module.new do
+          using refinement
+          result = "#{1}"
+        end
+
+        result.should == "1"
+      end
+    end
+
+    ruby_version_is "2.5" do
+      it "is honored by string interpolation" do
+        refinement = Module.new do
+          refine Integer do
+            def to_s
+              "foo"
+            end
+          end
+        end
+
+        result = nil
+        Module.new do
+          using refinement
+          result = "#{1}"
+        end
+
+        result.should == "foo"
+      end
+    end
+
     it "is honored by Kernel#binding" do
       refinement = Module.new do
         refine String do
diff --git a/spec/ruby/core/process/setsid_spec.rb b/spec/ruby/core/process/setsid_spec.rb
index abb75f8225..5f060ef218 100644
--- a/spec/ruby/core/process/setsid_spec.rb
+++ b/spec/ruby/core/process/setsid_spec.rb
@@ -22,7 +22,7 @@ describe "Process.setsid" do
       read2.close
       pgid_child = Integer(read.gets)
       read.close
-      platform_is_not :aix do
+      platform_is_not :aix, :openbsd do
         # AIX does not allow Process.getsid(pid)
         # if pid is in a different session.
         pgid = Process.getsid(pid)
diff --git a/spec/ruby/core/process/spawn_spec.rb b/spec/ruby/core/process/spawn_spec.rb
index 330ec8fcd8..9e34713757 100644
--- a/spec/ruby/core/process/spawn_spec.rb
+++ b/spec/ruby/core/process/spawn_spec.rb
@@ -595,8 +595,10 @@ describe "Process.spawn" do
     end
   end
 
-  it "raises an Errno::EACCES when passed a directory" do
-    lambda { Process.spawn File.dirname(__FILE__) }.should raise_error(Errno::EACCES)
+  it "raises an Errno::EACCES or Errno::EISDIR when passed a directory" do
+    lambda { Process.spawn File.dirname(__FILE__) }.should raise_error(SystemCallError) { |e|
+      [Errno::EACCES, Errno::EISDIR].should include(e.class)
+    }
   end
 
   it "raises an ArgumentError when passed a string key in options" do
diff --git a/spec/ruby/core/string/delete_prefix_spec.rb b/spec/ruby/core/string/delete_prefix_spec.rb
new file mode 100644
index 0000000000..94d486eace
--- /dev/null
+++ b/spec/ruby/core/string/delete_prefix_spec.rb
@@ -0,0 +1,81 @@
+# -*- encoding: utf-8 -*-
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes.rb', __FILE__)
+
+ruby_version_is '2.5' do
+  describe "String#delete_prefix" do
+    it "returns a copy of the string, with the given prefix removed" do
+      'hello'.delete_prefix('hell').should == 'o'
+      'hello'.delete_prefix('hello').should == ''
+    end
+
+    it "returns a copy of the string, when the prefix isn't found" do
+      s = 'hello'
+      r = s.delete_prefix('hello!')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_prefix('ell')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_prefix('')
+      r.should_not equal s
+      r.should == s
+    end
+
+    it "taints resulting strings when other is tainted" do
+      'hello'.taint.delete_prefix('hell').tainted?.should == true
+      'hello'.taint.delete_prefix('').tainted?.should == true
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_prefix('hell')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'hell'
+      'hello'.delete_prefix(o).should == 'o'
+    end
+
+    it "returns a subclass instance when called on a subclass instance" do
+      s = StringSpecs::MyString.new('hello')
+      s.delete_prefix('hell').should be_an_instance_of(StringSpecs::MyString)
+    end
+  end
+
+  describe "String#delete_prefix!" do
+    it "removes the found prefix" do
+      s = 'hello'
+      s.delete_prefix!('hell').should equal(s)
+      s.should == 'o'
+    end
+
+    it "returns nil if no change is made" do
+      s = 'hello'
+      s.delete_prefix!('ell').should == nil
+      s.delete_prefix!('').should == nil
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_prefix!('hell')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'hell'
+      'hello'.delete_prefix!(o).should == 'o'
+    end
+
+    it "raises a RuntimeError when self is frozen" do
+      lambda { 'hello'.freeze.delete_prefix!('hell') }.should raise_error(RuntimeError)
+      lambda { 'hello'.freeze.delete_prefix!('') }.should raise_error(RuntimeError)
+      lambda { ''.freeze.delete_prefix!('') }.should raise_error(RuntimeError)
+    end
+  end
+end
diff --git a/spec/ruby/core/string/delete_suffix_spec.rb b/spec/ruby/core/string/delete_suffix_spec.rb
new file mode 100644
index 0000000000..49689a8da1
--- /dev/null
+++ b/spec/ruby/core/string/delete_suffix_spec.rb
@@ -0,0 +1,81 @@
+# -*- encoding: utf-8 -*-
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes.rb', __FILE__)
+
+ruby_version_is '2.5' do
+  describe "String#delete_suffix" do
+    it "returns a copy of the string, with the given suffix removed" do
+      'hello'.delete_suffix('ello').should == 'h'
+      'hello'.delete_suffix('hello').should == ''
+    end
+
+    it "returns a copy of the string, when the suffix isn't found" do
+      s = 'hello'
+      r = s.delete_suffix('!hello')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_suffix('ell')
+      r.should_not equal s
+      r.should == s
+      r = s.delete_suffix('')
+      r.should_not equal s
+      r.should == s
+    end
+
+    it "taints resulting strings when other is tainted" do
+      'hello'.taint.delete_suffix('ello').tainted?.should == true
+      'hello'.taint.delete_suffix('').tainted?.should == true
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_suffix('ello')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'ello'
+      'hello'.delete_suffix(o).should == 'h'
+    end
+
+    it "returns a subclass instance when called on a subclass instance" do
+      s = StringSpecs::MyString.new('hello')
+      s.delete_suffix('ello').should be_an_instance_of(StringSpecs::MyString)
+    end
+  end
+
+  describe "String#delete_suffix!" do
+    it "removes the found prefix" do
+      s = 'hello'
+      s.delete_suffix!('ello').should equal(s)
+      s.should == 'h'
+    end
+
+    it "returns nil if no change is made" do
+      s = 'hello'
+      s.delete_suffix!('ell').should == nil
+      s.delete_suffix!('').should == nil
+    end
+
+    it "doesn't set $~" do
+      $~ = nil
+
+      'hello'.delete_suffix!('ello')
+      $~.should == nil
+    end
+
+    it "calls to_str on its argument" do
+      o = mock('x')
+      o.should_receive(:to_str).and_return 'ello'
+      'hello'.delete_suffix!(o).should == 'h'
+    end
+
+    it "raises a RuntimeError when self is frozen" do
+      lambda { 'hello'.freeze.delete_suffix!('ello') }.should raise_error(RuntimeError)
+      lambda { 'hello'.freeze.delete_suffix!('') }.should raise_error(RuntimeError)
+      lambda { ''.freeze.delete_suffix!('') }.should raise_error(RuntimeError)
+    end
+  end
+end
diff --git a/spec/ruby/core/string/start_with_spec.rb b/spec/ruby/core/string/start_with_spec.rb
index b85081037d..1b27fdaed7 100644
--- a/spec/ruby/core/string/start_with_spec.rb
+++ b/spec/ruby/core/string/start_with_spec.rb
@@ -28,9 +28,9 @@ describe "String#start_with?" do
 
   it "ignores arguments not convertible to string" do
     "hello".start_with?().should be_false
-    lambda { "hello".start_with?(1) }.should  raise_error(TypeError)
-    lambda { "hello".start_with?(["h"]) }.should  raise_error(TypeError)
-    lambda { "hello".start_with?(1, nil, "h").should }.should raise_error(TypeError)
+    lambda { "hello".start_with?(1) }.should raise_error(TypeError)
+    lambda { "hello".start_with?(["h"]) }.should raise_error(TypeError)
+    lambda { "hello".start_with?(1, nil, "h") }.should raise_error(TypeError)
   end
 
   it "uses only the needed arguments" do
diff --git a/spec/ruby/core/struct/new_spec.rb b/spec/ruby/core/struct/new_spec.rb
index db168ba279..f43e764cb8 100644
--- a/spec/ruby/core/struct/new_spec.rb
+++ b/spec/ruby/core/struct/new_spec.rb
@@ -60,7 +60,18 @@ describe "Struct.new" do
     lambda { Struct.new(:animal, nil)                  }.should raise_error(TypeError)
     lambda { Struct.new(:animal, true)                 }.should raise_error(TypeError)
     lambda { Struct.new(:animal, ['chris', 'evan'])    }.should raise_error(TypeError)
-    lambda { Struct.new(:animal, { name: 'chris' }) }.should raise_error(ArgumentError)
+  end
+
+  ruby_version_is ""..."2.5" do
+    it "raises a TypeError if an argument is a Hash" do
+      lambda { Struct.new(:animal, { name: 'chris' }) }.should raise_error(TypeError)
+    end
+  end
+
+  ruby_version_is "2.5" do
+    it "raises a ArgumentError if passed a Hash with an unknown key" do
+      lambda { Struct.new(:animal, { name: 'chris' }) }.should raise_error(ArgumentError)
+    end
   end
 
   it "raises a TypeError if object is not a Symbol" do
diff --git a/spec/ruby/core/time/at_spec.rb b/spec/ruby/core/time/at_spec.rb
index 40c729316e..6883a8d074 100644
--- a/spec/ruby/core/time/at_spec.rb
+++ b/spec/ruby/core/time/at_spec.rb
@@ -142,4 +142,60 @@ describe "Time.at" do
       lambda { Time.at(Time.now, 500000) }.should raise_error(TypeError)
     end
   end
+
+  ruby_version_is "2.5" do
+    describe "passed [Time, Numeric, format]" do
+      context ":nanosecond format" do
+        it "traits second argument as nanoseconds" do
+          Time.at(0, 123456789, :nanosecond).nsec.should == 123456789
+        end
+      end
+
+      context ":nsec format" do
+        it "traits second argument as nanoseconds" do
+          Time.at(0, 123456789, :nsec).nsec.should == 123456789
+        end
+      end
+
+      context ":microsecond format" do
+        it "traits second argument as microseconds" do
+          Time.at(0, 123456, :microsecond).nsec.should == 123456000
+        end
+      end
+
+      context ":usec format" do
+        it "traits second argument as microseconds" do
+          Time.at(0, 123456, :usec).nsec.should == 123456000
+        end
+      end
+
+      context ":millisecond format" do
+        it "traits second argument as milliseconds" do
+          Time.at(0, 123, :millisecond).nsec.should == 123000000
+        end
+      end
+
+      context "not supported format" do
+        it "raises ArgumentError" do
+          ->() { Time.at(0, 123456, 2) }.should raise_error(ArgumentError)
+          ->() { Time.at(0, 123456, nil) }.should raise_error(ArgumentError)
+          ->() { Time.at(0, 123456, :invalid) }.should raise_error(ArgumentError)
+        end
+
+        it "does not try to convert format to Symbol with #to_sym" do
+          format = "usec"
+          format.should_not_receive(:to_sym)
+          -> () { Time.at(0, 123456, format) }.should raise_error(ArgumentError)
+        end
+      end
+
+      it "supports Float second argument" do
+        Time.at(0, 123456789.500, :nanosecond).nsec.should == 123456789
+        Time.at(0, 123456789.500, :nsec).nsec.should == 123456789
+        Time.at(0, 123456.500, :microsecond).nsec.should == 123456500
+        Time.at(0, 123456.500, :usec).nsec.should == 123456500
+        Time.at(0, 123.500, :millisecond).nsec.should == 123500000
+      end
+    end
+  end
 end
diff --git a/spec/ruby/language/constants_spec.rb b/spec/ruby/language/constants_spec.rb
index 45d87ce52f..1f1e254fb8 100644
--- a/spec/ruby/language/constants_spec.rb
+++ b/spec/ruby/language/constants_spec.rb
@@ -425,6 +425,28 @@ describe "Constant resolution within a singleton class (class << obj)" do
   end
 end
 
+describe "top-level constant lookup" do
+  context "on a class" do
+    ruby_version_is "" ... "2.5" do
+      it "searches Object successfully after searching other scopes" do
+        ->() {
+          String::Hash.should == Hash
+        }.should complain(/toplevel constant Hash referenced by/)
+      end
+    end
+
+    ruby_version_is "2.5" do
+      it "does not search Object after searching other scopes" do
+        ->() { String::Hash }.should raise_error(NameError)
+      end
+    end
+  end
+
+  it "searches Object unsuccessfully when searches on a module" do
+    ->() { Enumerable::Hash }.should raise_error(NameError)
+  end
+end
+
 describe "Module#private_constant marked constants" do
 
   it "remain private even when updated" do
diff --git a/spec/ruby/language/ensure_spec.rb b/spec/ruby/language/ensure_spec.rb
index ae04feb739..1d99dcf5f2 100644
--- a/spec/ruby/language/ensure_spec.rb
+++ b/spec/ruby/language/ensure_spec.rb
@@ -7,50 +7,44 @@ describe "An ensure block inside a begin block" do
   end
 
   it "is executed when an exception is raised in it's corresponding begin block" do
-    begin
-      lambda {
-        begin
-          ScratchPad << :begin
-          raise "An exception occurred!"
-        ensure
-          ScratchPad << :ensure
-        end
-      }.should raise_error(RuntimeError)
+    lambda {
+      begin
+        ScratchPad << :begin
+        raise EnsureSpec::Error
+      ensure
+        ScratchPad << :ensure
+      end
+    }.should raise_error(EnsureSpec::Error)
 
-      ScratchPad.recorded.should == [:begin, :ensure]
-    end
+    ScratchPad.recorded.should == [:begin, :ensure]
   end
 
   it "is executed when an exception is raised and rescued in it's corresponding begin block" do
     begin
+      ScratchPad << :begin
+      raise "An exception occurred!"
+    rescue
+      ScratchPad << :rescue
+    ensure
+      ScratchPad << :ensure
+    end
+
+    ScratchPad.recorded.should == [:begin, :rescue, :ensure]
+  end
+
+  it "is executed even when a symbol is thrown in it's corresponding begin block" do
+    catch(:symbol) do
       begin
         ScratchPad << :begin
-        raise "An exception occurred!"
+        throw(:symbol)
       rescue
         ScratchPad << :rescue
       ensure
         ScratchPad << :ensure
       end
-
-      ScratchPad.recorded.should == [:begin, :rescue, :ensure]
     end
-  end
 
-  it "is executed even when a symbol is thrown in it's corresponding begin block" do
-    begin
-      catch(:symbol) do
-        begin
-          ScratchPad << :begin
-          throw(:symbol)
-        rescue
-          ScratchPad << :rescue
-        ensure
-          ScratchPad << :ensure
-        end
-      end
-
-      ScratchPad.recorded.should == [:begin, :ensure]
-    end
+    ScratchPad.recorded.should == [:begin, :ensure]
   end
 
   it "is executed when nothing is raised or thrown in it's corresponding begin block" do
@@ -102,7 +96,7 @@ describe "An ensure block inside a method" do
   end
 
   it "is executed when an exception is raised in the method" do
-    lambda { @obj.raise_in_method_with_ensure }.should raise_error(RuntimeError)
+    lambda { @obj.raise_in_method_with_ensure }.should raise_error(EnsureSpec::Error)
     @obj.executed.should == [:method, :ensure]
   end
 
@@ -124,3 +118,176 @@ describe "An ensure block inside a method" do
     @obj.explicit_return_in_method_with_ensure.should == :ensure
   end
 end
+
+describe "An ensure block inside a class" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  it "is executed when an exception is raised" do
+    lambda {
+      eval <<-ruby
+        class EnsureInClassExample
+          ScratchPad << :class
+          raise EnsureSpec::Error
+        ensure
+          ScratchPad << :ensure
+        end
+      ruby
+    }.should raise_error(EnsureSpec::Error)
+
+    ScratchPad.recorded.should == [:class, :ensure]
+  end
+
+  it "is executed when an exception is raised and rescued" do
+    eval <<-ruby
+      class EnsureInClassExample
+        ScratchPad << :class
+        raise
+      rescue
+        ScratchPad << :rescue
+      ensure
+        ScratchPad << :ensure
+      end
+    ruby
+
+    ScratchPad.recorded.should == [:class, :rescue, :ensure]
+  end
+
+  it "is executed even when a symbol is thrown" do
+    catch(:symbol) do
+      eval <<-ruby
+        class EnsureInClassExample
+          ScratchPad << :class
+          throw(:symbol)
+        rescue
+          ScratchPad << :rescue
+        ensure
+          ScratchPad << :ensure
+        end
+      ruby
+    end
+
+    ScratchPad.recorded.should == [:class, :ensure]
+  end
+
+  it "is executed when nothing is raised or thrown" do
+    eval <<-ruby
+      class EnsureInClassExample
+        ScratchPad << :class
+      rescue
+        ScratchPad << :rescue
+      ensure
+        ScratchPad << :ensure
+      end
+    ruby
+
+    ScratchPad.recorded.should == [:class, :ensure]
+  end
+
+  it "has no return value" do
+    result = eval <<-ruby
+      class EnsureInClassExample
+        :class
+      ensure
+        :ensure
+      end
+    ruby
+
+    result.should == :class
+  end
+end
+
+describe "An ensure block inside {} block" do
+  it "is not allowed" do
+    lambda {
+      eval <<-ruby
+        lambda {
+          raise
+        ensure
+        }
+      ruby
+    }.should raise_error(SyntaxError)
+  end
+end
+
+ruby_version_is "2.5" do
+  describe "An ensure block inside 'do end' block" do
+    before :each do
+      ScratchPad.record []
+    end
+
+    it "is executed when an exception is raised in it's corresponding begin block" do
+      lambda {
+        eval(<<-ruby).call
+          lambda do
+            ScratchPad << :begin
+            raise EnsureSpec::Error
+          ensure
+            ScratchPad << :ensure
+          end
+        ruby
+      }.should raise_error(EnsureSpec::Error)
+
+      ScratchPad.recorded.should == [:begin, :ensure]
+    end
+
+    it "is executed when an exception is raised and rescued in it's corresponding begin block" do
+      eval(<<-ruby).call
+        lambda do
+          ScratchPad << :begin
+          raise "An exception occurred!"
+        rescue
+          ScratchPad << :rescue
+        ensure
+          ScratchPad << :ensure
+        end
+      ruby
+
+      ScratchPad.recorded.should == [:begin, :rescue, :ensure]
+    end
+
+    it "is executed even when a symbol is thrown in it's corresponding begin block" do
+      catch(:symbol) do
+        eval(<<-ruby).call
+          lambda do
+            ScratchPad << :begin
+            throw(:symbol)
+          rescue
+            ScratchPad << :rescue
+          ensure
+            ScratchPad << :ensure
+          end
+        ruby
+      end
+
+      ScratchPad.recorded.should == [:begin, :ensure]
+    end
+
+    it "is executed when nothing is raised or thrown in it's corresponding begin block" do
+      eval(<<-ruby).call
+        lambda do
+          ScratchPad << :begin
+        rescue
+          ScratchPad << :rescue
+        ensure
+          ScratchPad << :ensure
+        end
+      ruby
+
+      ScratchPad.recorded.should == [:begin, :ensure]
+    end
+
+    it "has no return value" do
+      result = eval(<<-ruby).call
+        lambda do
+          :begin
+        ensure
+          :ensure
+        end
+      ruby
+
+      result.should == :begin
+    end
+  end
+end
diff --git a/spec/ruby/language/fixtures/ensure.rb b/spec/ruby/language/fixtures/ensure.rb
index 0dad7d8401..d1a9da37b8 100644
--- a/spec/ruby/language/fixtures/ensure.rb
+++ b/spec/ruby/language/fixtures/ensure.rb
@@ -8,7 +8,7 @@ module EnsureSpec
 
     def raise_in_method_with_ensure
       @executed << :method
-      raise "An Exception"
+      raise EnsureSpec::Error
     ensure
       @executed << :ensure
     end
@@ -70,3 +70,8 @@ module EnsureSpec
     end
   end
 end
+
+module EnsureSpec
+  class Error < RuntimeError
+  end
+end
diff --git a/spec/ruby/language/rescue_spec.rb b/spec/ruby/language/rescue_spec.rb
index d7042b7973..0dc8894740 100644
--- a/spec/ruby/language/rescue_spec.rb
+++ b/spec/ruby/language/rescue_spec.rb
@@ -31,6 +31,28 @@ describe "The rescue keyword" do
     end
   end
 
+  it "returns value from `rescue` if an exception was raised" do
+    begin
+      raise
+    rescue
+      :caught
+    end.should == :caught
+  end
+
+  it "returns value from `else` section if no exceptions were raised" do
+    result = begin
+      :begin
+    rescue
+      :rescue
+    else
+      :else
+    ensure
+      :ensure
+    end
+
+    result.should == :else
+  end
+
   it "can rescue multiple raised exceptions with a single rescue block" do
     [lambda{raise ArbitraryException}, lambda{raise SpecificExampleException}].map do |block|
       begin
@@ -94,6 +116,32 @@ describe "The rescue keyword" do
     end.should raise_error(OtherCustomException)
   end
 
+  it "can rescue different types of exceptions in different ways" do
+    begin
+      raise Exception
+    rescue RuntimeError
+    rescue StandardError
+    rescue Exception
+      ScratchPad << :exception
+    end
+
+    ScratchPad.recorded.should == [:exception]
+  end
+
+  it "rescues exception within the first suitable section in order of declaration" do
+    begin
+      raise StandardError
+    rescue RuntimeError
+      ScratchPad << :runtime_error
+    rescue StandardError
+      ScratchPad << :standard_error
+    rescue Exception
+      ScratchPad << :exception
+    end
+
+    ScratchPad.recorded.should == [:standard_error]
+  end
+
   it "will execute an else block only if no exceptions were raised" do
     result = begin
       ScratchPad << :one
@@ -147,6 +195,20 @@ describe "The rescue keyword" do
     ScratchPad.recorded.should == [:one, :else_ran, :ensure_ran, :outside_begin]
   end
 
+  it "will execute an else block even without rescue and ensure" do
+    lambda {
+      eval <<-ruby
+        begin
+          ScratchPad << :begin
+        else
+          ScratchPad << :else
+        end
+      ruby
+    }.should complain(/else without rescue is useless/)
+
+    ScratchPad.recorded.should == [:begin, :else]
+  end
+
   it "will not execute an else block if an exception was raised" do
     result = begin
       ScratchPad << :one
@@ -223,14 +285,31 @@ describe "The rescue keyword" do
     a.should == 'ac'
   end
 
-  it "without classes will not rescue Exception" do
-    lambda do
+  context "without rescue expression" do
+    it "will rescue only StandardError and its subclasses" do
       begin
-        raise Exception
+        raise StandardError
       rescue
-        'Exception wrongly rescued'
+        ScratchPad << :caught
       end
-    end.should raise_error(Exception)
+
+      ScratchPad.recorded.should == [:caught]
+    end
+
+    it "will not rescue exceptions except StandardError" do
+      [ Exception.new, NoMemoryError.new, ScriptError.new, SecurityError.new,
+        SignalException.new('INT'), SystemExit.new, SystemStackError.new
+      ].each do |exception|
+        lambda {
+          begin
+            raise exception
+          rescue
+            ScratchPad << :caught
+          end
+        }.should raise_error(exception.class)
+      end
+      ScratchPad.recorded.should == []
+    end
   end
 
   it "uses === to compare against rescued classes" do
@@ -279,7 +358,7 @@ describe "The rescue keyword" do
     invalid_rescuer = Object.new
     begin
       :foo
-    rescue rescuer
+    rescue invalid_rescuer
     end.should == :foo
   end
 
@@ -291,6 +370,44 @@ describe "The rescue keyword" do
     end.should == :expected
   end
 
+  it "allows rescue in class" do
+    eval <<-ruby
+      class RescueInClassExample
+        raise SpecificExampleException
+      rescue SpecificExampleException
+        ScratchPad << :caught
+      end
+    ruby
+
+    ScratchPad.recorded.should == [:caught]
+  end
+
+  it "does not allow rescue in {} block" do
+    lambda {
+      eval <<-ruby
+        lambda {
+          raise SpecificExampleException
+        rescue SpecificExampleException
+          :caught
+        }
+      ruby
+    }.should raise_error(SyntaxError)
+  end
+
+  ruby_version_is "2.5" do
+    it "allows rescue in 'do end' block" do
+      lambda = eval <<-ruby
+        lambda do
+          raise SpecificExampleException
+        rescue SpecificExampleException
+          ScratchPad << :caught
+        end.call
+      ruby
+
+      ScratchPad.recorded.should == [:caught]
+    end
+  end
+
   ruby_version_is ""..."2.4" do
     it "fails when using 'rescue' in method arguments" do
       lambda { eval '1.+ (1 rescue 1)' }.should raise_error(SyntaxError)
@@ -305,6 +422,31 @@ describe "The rescue keyword" do
 
     it "requires the 'rescue' in method arguments to be wrapped in parens" do
       lambda { eval '1.+(1 rescue 1)' }.should raise_error(SyntaxError)
+      eval('1.+((1 rescue 1))').should == 2
+    end
+  end
+
+  describe "inline form" do
+    it "can be inlined" do
+      a = 1/0 rescue 1
+      a.should == 1
+    end
+
+    it "doesn't except rescue expression" do
+      lambda {
+        eval <<-ruby
+          a = 1 rescue RuntimeError 2
+        ruby
+      }.should raise_error(SyntaxError)
+    end
+
+    it "rescues only StandardError and its subclasses" do
+      a = raise(StandardError) rescue 1
+      a.should == 1
+
+      lambda {
+        a = raise(Exception) rescue 1
+      }.should raise_error(Exception)
     end
   end
 end
diff --git a/spec/ruby/library/date/shared/valid_jd.rb b/spec/ruby/library/date/shared/valid_jd.rb
index d8a35992b3..bd71f5abba 100644
--- a/spec/ruby/library/date/shared/valid_jd.rb
+++ b/spec/ruby/library/date/shared/valid_jd.rb
@@ -1,8 +1,8 @@
 describe :date_valid_jd?, shared: true do
   it "returns true if passed any value other than nil" do
     Date.send(@method, -100).should be_true
-    Date.send(@method, :number).should    be_true
-    Date.send(@method, Rational(1,2)).should  be_true
+    Date.send(@method, :number).should be_true
+    Date.send(@method, Rational(1,2)).should be_true
   end
 
   it "returns false if passed nil" do
diff --git a/spec/ruby/library/matrix/build_spec.rb b/spec/ruby/library/matrix/build_spec.rb
index 29fd72206f..4f80ed2b99 100644
--- a/spec/ruby/library/matrix/build_spec.rb
+++ b/spec/ruby/library/matrix/build_spec.rb
@@ -24,7 +24,7 @@ describe "Matrix.build" do
 
   it "returns an Enumerator is no block is given" do
     enum = Matrix.build(2, 1)
-    enum.should  be_an_instance_of(Enumerator)
+    enum.should be_an_instance_of(Enumerator)
     enum.each{1}.should == Matrix[[1], [1]]
   end
 
diff --git a/spec/ruby/library/set/case_compare_spec.rb b/spec/ruby/library/set/case_compare_spec.rb
new file mode 100644
index 0000000000..f47e4e20c2
--- /dev/null
+++ b/spec/ruby/library/set/case_compare_spec.rb
@@ -0,0 +1,15 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../shared/include', __FILE__)
+require 'set'
+
+ruby_version_is "2.5" do
+  describe "Set#===" do
+    it_behaves_like :set_include, :===
+
+    it "is an alias for include?" do
+      set = Set.new
+      set.method(:===).should == set.method(:include?)
+    end
+  end
+end
+
diff --git a/spec/ruby/library/set/inspect_spec.rb b/spec/ruby/library/set/inspect_spec.rb
index 8a6c565c2e..ef91b11645 100644
--- a/spec/ruby/library/set/inspect_spec.rb
+++ b/spec/ruby/library/set/inspect_spec.rb
@@ -1,18 +1,7 @@
 require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../shared/inspect', __FILE__)
 require 'set'
 
 describe "Set#inspect" do
-  it "returns a String representation of self" do
-    Set[].inspect.should be_kind_of(String)
-    Set[nil, false, true].inspect.should be_kind_of(String)
-    Set[1, 2, 3].inspect.should be_kind_of(String)
-    Set["1", "2", "3"].inspect.should be_kind_of(String)
-    Set[:a, "b", Set[?c]].inspect.should be_kind_of(String)
-  end
-
-  it "correctly handles self-references" do
-    (set = Set[]) << set
-    set.inspect.should be_kind_of(String)
-    set.inspect.should include("#<Set: {...}>")
-  end
+  it_behaves_like :set_inspect, :inspect
 end
diff --git a/spec/ruby/library/set/shared/include.rb b/spec/ruby/library/set/shared/include.rb
index d41f8f4102..b4d95cde24 100644
--- a/spec/ruby/library/set/shared/include.rb
+++ b/spec/ruby/library/set/shared/include.rb
@@ -4,4 +4,26 @@ describe :set_include, shared: true do
     set.send(@method, :a).should be_true
     set.send(@method, :e).should be_false
   end
+
+  describe "member equality" do
+    it "is checked using both #hash and #eql?" do
+      obj = Object.new
+      obj_another = Object.new
+
+      def obj.hash; 42 end
+      def obj_another.hash; 42 end
+      def obj_another.eql?(o) hash == o.hash end
+
+      set = Set["a", "b", "c", obj]
+      set.send(@method, obj_another).should == true
+    end
+
+    it "is not checked using #==" do
+      obj = Object.new
+      set = Set["a", "b", "c"]
+
+      obj.should_not_receive(:==)
+      set.send(@method, obj)
+    end
+  end
 end
diff --git a/spec/ruby/library/set/shared/inspect.rb b/spec/ruby/library/set/shared/inspect.rb
new file mode 100644
index 0000000000..69fbdd12f6
--- /dev/null
+++ b/spec/ruby/library/set/shared/inspect.rb
@@ -0,0 +1,15 @@
+describe "set_inspect", shared: true do
+  it "returns a String representation of self" do
+    Set[].send(@method).should be_kind_of(String)
+    Set[nil, false, true].send(@method).should be_kind_of(String)
+    Set[1, 2, 3].send(@method).should be_kind_of(String)
+    Set["1", "2", "3"].send(@method).should be_kind_of(String)
+    Set[:a, "b", Set[?c]].send(@method).should be_kind_of(String)
+  end
+
+  it "correctly handles self-references" do
+    (set = Set[]) << set
+    set.send(@method).should be_kind_of(String)
+    set.send(@method).should include("#<Set: {...}>")
+  end
+end
diff --git a/spec/ruby/library/set/to_s_spec.rb b/spec/ruby/library/set/to_s_spec.rb
new file mode 100644
index 0000000000..f4c361f74f
--- /dev/null
+++ b/spec/ruby/library/set/to_s_spec.rb
@@ -0,0 +1,13 @@
+require File.expand_path('../shared/inspect', __FILE__)
+require 'set'
+
+ruby_version_is "2.5" do
+  describe "Set#to_s" do
+    it_behaves_like :set_inspect, :to_s
+
+    it "is an alias of inspect" do
+      set = Set.new
+      set.method(:to_s).should == set.method(:inspect)
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/udpsocket/new_spec.rb b/spec/ruby/library/socket/udpsocket/new_spec.rb
index 5a2e4e1f31..f13e605959 100644
--- a/spec/ruby/library/socket/udpsocket/new_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/new_spec.rb
@@ -26,7 +26,9 @@ describe 'UDPSocket.new' do
     @socket.should be_an_instance_of(UDPSocket)
   end
 
-  it 'raises Errno::EAFNOSUPPORT if unsupported family passed' do
-    lambda { UDPSocket.new(-1) }.should raise_error(Errno::EAFNOSUPPORT)
+  it 'raises Errno::EAFNOSUPPORT or Errno::EPROTONOSUPPORT if unsupported family passed' do
+    lambda { UDPSocket.new(-1) }.should raise_error(SystemCallError) { |e|
+      [Errno::EAFNOSUPPORT, Errno::EPROTONOSUPPORT].should include(e.class)
+    }
   end
 end
diff --git a/spec/ruby/library/stringio/pos_spec.rb b/spec/ruby/library/stringio/pos_spec.rb
index 59d0a43f12..d5f3c3ab95 100644
--- a/spec/ruby/library/stringio/pos_spec.rb
+++ b/spec/ruby/library/stringio/pos_spec.rb
@@ -17,7 +17,7 @@ describe "StringIO#pos=" do
   end
 
   it "raises an EINVAL if given a negative argument" do
-    lambda { @io.pos = -10 }.should  raise_error(Errno::EINVAL)
+    lambda { @io.pos = -10 }.should raise_error(Errno::EINVAL)
   end
 
   it "updates the current byte offset after reaching EOF" do