diff --git a/spec/mspec/lib/mspec/commands/mspec-run.rb b/spec/mspec/lib/mspec/commands/mspec-run.rb
index 4d8f4d9984e8..064c177d69b9 100644
--- a/spec/mspec/lib/mspec/commands/mspec-run.rb
+++ b/spec/mspec/lib/mspec/commands/mspec-run.rb
@@ -32,6 +32,7 @@ def options(argv = ARGV)
     options.chdir
     options.prefix
     options.configure { |f| load f }
+    options.env
     options.randomize
     options.repeat
     options.pretend
diff --git a/spec/mspec/lib/mspec/utils/options.rb b/spec/mspec/lib/mspec/utils/options.rb
index 3b5962dbe6e7..23cf915e66d2 100644
--- a/spec/mspec/lib/mspec/utils/options.rb
+++ b/spec/mspec/lib/mspec/utils/options.rb
@@ -204,6 +204,13 @@ def configure(&block)
        "Load FILE containing configuration options", &block)
   end
 
+  def env
+    on("--env", "KEY=VALUE", "Set environment variable") do |env|
+      key, value = env.split('=', 2)
+      ENV[key] = value
+    end
+  end
+
   def targets
     on("-t", "--target", "TARGET",
        "Implementation to run the specs, where TARGET is:") do |t|
@@ -484,6 +491,7 @@ def debug
 
   def all
     configure {}
+    env
     targets
     formatters
     filters
diff --git a/spec/mspec/tool/sync/sync-rubyspec.rb b/spec/mspec/tool/sync/sync-rubyspec.rb
index 13f1d8004dcb..effccc1567c1 100644
--- a/spec/mspec/tool/sync/sync-rubyspec.rb
+++ b/spec/mspec/tool/sync/sync-rubyspec.rb
@@ -23,6 +23,8 @@
 CHECK_LAST_MERGE = !MSPEC && ENV['CHECK_LAST_MERGE'] != 'false'
 TEST_MASTER = ENV['TEST_MASTER'] != 'false'
 
+ONLY_FILTER = ENV['ONLY_FILTER'] == 'true'
+
 MSPEC_REPO = File.expand_path("../../..", __FILE__)
 raise MSPEC_REPO if !Dir.exist?(MSPEC_REPO) or !Dir.exist?("#{MSPEC_REPO}/.git")
 
@@ -230,15 +232,17 @@ def main(impls)
     impl = RubyImplementation.new(impl, data)
     update_repo(impl)
     filter_commits(impl)
-    rebase_commits(impl)
-    if new_commits?(impl)
-      test_new_specs
-      verify_commits(impl)
-      fast_forward_master(impl)
-      check_ci
-    else
-      STDERR.puts "#{BRIGHT_YELLOW}No new commits#{RESET}"
-      fast_forward_master(impl)
+    unless ONLY_FILTER
+      rebase_commits(impl)
+      if new_commits?(impl)
+        test_new_specs
+        verify_commits(impl)
+        fast_forward_master(impl)
+        check_ci
+      else
+        STDERR.puts "#{BRIGHT_YELLOW}No new commits#{RESET}"
+        fast_forward_master(impl)
+      end
     end
   end
 end
diff --git a/spec/ruby/command_line/dash_v_spec.rb b/spec/ruby/command_line/dash_v_spec.rb
index 747db7f75588..d30efa37d68c 100644
--- a/spec/ruby/command_line/dash_v_spec.rb
+++ b/spec/ruby/command_line/dash_v_spec.rb
@@ -9,6 +9,7 @@
       ruby_exe(nil, args: '-v').sub("+PRISM ", "").should include(RUBY_DESCRIPTION.sub("+PRISM ", ""))
     end unless (defined?(RubyVM::YJIT) && RubyVM::YJIT.enabled?) ||
                (defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled?) ||
+               (ENV['RUBY_GC_LIBRARY'] && ENV['RUBY_GC_LIBRARY'].length > 0) ||
                (ENV['RUBY_MN_THREADS'] == '1')
   end
 end
diff --git a/spec/ruby/command_line/rubyopt_spec.rb b/spec/ruby/command_line/rubyopt_spec.rb
index 38e29c0d2145..e940f912af8f 100644
--- a/spec/ruby/command_line/rubyopt_spec.rb
+++ b/spec/ruby/command_line/rubyopt_spec.rb
@@ -25,12 +25,12 @@
   guard -> { RbConfig::CONFIG["CROSS_COMPILING"] != "yes" } do
     it "prints the version number for '-v'" do
       ENV["RUBYOPT"] = '-v'
-      ruby_exe("").sub("+PRISM ", "")[/\A.*/].should == RUBY_DESCRIPTION.sub("+PRISM ", "")
+      ruby_exe("").sub("+PRISM ", "").sub(/\+GC(\[\w+\]\s|\s)?/, "")[/\A.*/].should == RUBY_DESCRIPTION.sub("+PRISM ", "").sub(/\+GC(\[\w+\]\s|\s)?/, "")
     end
 
     it "ignores whitespace around the option" do
       ENV["RUBYOPT"] = ' -v '
-      ruby_exe("").sub("+PRISM ", "")[/\A.*/].should == RUBY_DESCRIPTION.sub("+PRISM ", "")
+      ruby_exe("").sub("+PRISM ", "").sub(/\+GC(\[\w+\]\s|\s)?/, "")[/\A.*/].should == RUBY_DESCRIPTION.sub("+PRISM ", "").sub(/\+GC(\[\w+\]\s|\s)?/, "")
     end
   end
 
diff --git a/spec/ruby/core/basicobject/equal_spec.rb b/spec/ruby/core/basicobject/equal_spec.rb
index 3c1ad56d4ab5..ce28eaed9554 100644
--- a/spec/ruby/core/basicobject/equal_spec.rb
+++ b/spec/ruby/core/basicobject/equal_spec.rb
@@ -11,8 +11,10 @@
   it "is unaffected by overriding __id__" do
     o1 = mock("object")
     o2 = mock("object")
-    def o1.__id__; 10; end
-    def o2.__id__; 10; end
+    suppress_warning {
+      def o1.__id__; 10; end
+      def o2.__id__; 10; end
+    }
     o1.equal?(o2).should be_false
   end
 
diff --git a/spec/ruby/core/exception/system_call_error_spec.rb b/spec/ruby/core/exception/system_call_error_spec.rb
index 7235aa9c268c..f6995d3c5ec3 100644
--- a/spec/ruby/core/exception/system_call_error_spec.rb
+++ b/spec/ruby/core/exception/system_call_error_spec.rb
@@ -96,11 +96,23 @@ def initialize
   end
 
   it "sets an 'unknown error' message when an unknown error number" do
-    SystemCallError.new(-1).message.should =~ /Unknown error(:)? -1/
+    platform_is_not :windows do
+      SystemCallError.new(-1).message.should =~ /Unknown error(:)? -1/
+    end
+
+    platform_is :windows do
+      SystemCallError.new(-1).message.should == "The operation completed successfully."
+    end
   end
 
   it "adds a custom error message to an 'unknown error' message when an unknown error number and a custom message specified" do
-    SystemCallError.new("custom message", -1).message.should =~ /Unknown error(:)? -1 - custom message/
+    platform_is_not :windows do
+      SystemCallError.new("custom message", -1).message.should =~ /Unknown error(:)? -1 - custom message/
+    end
+
+    platform_is :windows do
+      SystemCallError.new("custom message", -1).message.should == "The operation completed successfully. - custom message"
+    end
   end
 
   it "converts to Integer if errno is a Complex convertible to Integer" do
diff --git a/spec/ruby/core/integer/shared/exponent.rb b/spec/ruby/core/integer/shared/exponent.rb
index 15df518b7e49..5ef6d686d809 100644
--- a/spec/ruby/core/integer/shared/exponent.rb
+++ b/spec/ruby/core/integer/shared/exponent.rb
@@ -48,10 +48,18 @@
       (-1).send(@method, 4611686018427387905).should eql(-1)
     end
 
-    it "returns Float::INFINITY when the number is too big" do
-      -> {
-        2.send(@method, 427387904).should == Float::INFINITY
-      }.should complain(/warning: in a\*\*b, b may be too big/)
+    ruby_version_is ""..."3.4" do
+      it "returns Float::INFINITY when the number is too big" do
+        -> {
+          2.send(@method, 427387904).should == Float::INFINITY
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "raises an ArgumentError when the number is too big" do
+        -> { 100000000.send(@method, 1000000000) }.should raise_error(ArgumentError)
+      end
     end
 
     it "raises a ZeroDivisionError for 0 ** -1" do
@@ -108,13 +116,23 @@
       -> { @bignum.send(@method, :symbol) }.should raise_error(TypeError)
     end
 
-    it "switch to a Float when the values is too big" do
-      flt = nil
-      -> {
-        flt = @bignum.send(@method, @bignum)
-      }.should complain(/warning: in a\*\*b, b may be too big/)
-      flt.should be_kind_of(Float)
-      flt.infinite?.should == 1
+    ruby_version_is ""..."3.4" do
+      it "switch to a Float when the values is too big" do
+        flt = nil
+        -> {
+          flt = @bignum.send(@method, @bignum)
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+        flt.should be_kind_of(Float)
+        flt.infinite?.should == 1
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "does not switch to a Float when the values is too big" do
+        -> {
+          @bignum.send(@method, @bignum)
+        }.should raise_error(ArgumentError)
+      end
     end
 
     it "returns a complex number when negative and raised to a fractional power" do
diff --git a/spec/ruby/core/kernel/sleep_spec.rb b/spec/ruby/core/kernel/sleep_spec.rb
index 607764464fe3..4401e542563a 100644
--- a/spec/ruby/core/kernel/sleep_spec.rb
+++ b/spec/ruby/core/kernel/sleep_spec.rb
@@ -51,18 +51,15 @@ def o.divmod(*); [0, 0.001]; end
     t.value.should == 5
   end
 
-  quarantine! do # fails transiently on at least linux & darwin
-    it "sleeps with nanosecond precision" do
-      start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-      100.times do
-        sleep(0.0001)
-      end
-      end_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-
-      actual_duration = end_time - start_time
-      (actual_duration > 0.01).should == true # 100 * 0.0001 => 0.01
-      (actual_duration < 0.03).should == true
+  it "sleeps with nanosecond precision" do
+    start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    100.times do
+      sleep(0.0001)
     end
+    end_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+    actual_duration = end_time - start_time
+    actual_duration.should > 0.01 # 100 * 0.0001 => 0.01
   end
 
   ruby_version_is ""..."3.3" do
diff --git a/spec/ruby/core/module/deprecate_constant_spec.rb b/spec/ruby/core/module/deprecate_constant_spec.rb
index aabef934c4b5..ec0de6782ffa 100644
--- a/spec/ruby/core/module/deprecate_constant_spec.rb
+++ b/spec/ruby/core/module/deprecate_constant_spec.rb
@@ -44,6 +44,15 @@
     end
   end
 
+  ruby_bug '#20900', ''...'3.4' do
+    describe "when removing the deprecated module" do
+      it "warns with a message" do
+        @module.deprecate_constant :PUBLIC1
+        -> { @module.module_eval {remove_const :PUBLIC1} }.should complain(/warning: constant .+::PUBLIC1 is deprecated/)
+      end
+    end
+  end
+
   it "accepts multiple symbols and strings as constant names" do
     @module.deprecate_constant "PUBLIC1", :PUBLIC2
 
diff --git a/spec/ruby/core/process/status/bit_and_spec.rb b/spec/ruby/core/process/status/bit_and_spec.rb
index 97f768fdc1a9..f4a4328907d8 100644
--- a/spec/ruby/core/process/status/bit_and_spec.rb
+++ b/spec/ruby/core/process/status/bit_and_spec.rb
@@ -1,5 +1,35 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#&" do
-  it "needs to be reviewed for spec completeness"
+  it "returns a bitwise and of the integer status of an exited child" do
+    suppress_warning do
+      ruby_exe("exit(29)", exit_status: 29)
+      ($? & 0).should == 0
+      ($? & $?.to_i).should == $?.to_i
+
+      # Actual value is implementation specific
+      platform_is :linux do
+        # 29 == 0b11101
+        ($? & 0b1011100000000).should == 0b1010100000000
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises an ArgumentError if mask is negative" do
+      suppress_warning do
+        ruby_exe("exit(0)")
+        -> {
+          $? & -1
+        }.should raise_error(ArgumentError, 'negative mask value: -1')
+      end
+    end
+
+    it "shows a deprecation warning" do
+      ruby_exe("exit(0)")
+      -> {
+        $? & 0
+      }.should complain(/warning: Process::Status#& is deprecated and will be removed .*use other Process::Status predicates instead/)
+    end
+  end
 end
diff --git a/spec/ruby/core/process/status/right_shift_spec.rb b/spec/ruby/core/process/status/right_shift_spec.rb
index e9dda437e8b1..034ce348cbf9 100644
--- a/spec/ruby/core/process/status/right_shift_spec.rb
+++ b/spec/ruby/core/process/status/right_shift_spec.rb
@@ -1,5 +1,34 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#>>" do
-  it "needs to be reviewed for spec completeness"
+  it "returns a right shift of the integer status of an exited child" do
+    suppress_warning do
+      ruby_exe("exit(29)", exit_status: 29)
+      ($? >> 0).should == $?.to_i
+      ($? >> 1).should == $?.to_i >> 1
+
+      # Actual value is implementation specific
+      platform_is :linux do
+        ($? >> 8).should == 29
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises an ArgumentError if shift value is negative" do
+      suppress_warning do
+        ruby_exe("exit(0)")
+        -> {
+          $? >> -1
+        }.should raise_error(ArgumentError, 'negative shift value: -1')
+      end
+    end
+
+    it "shows a deprecation warning" do
+      ruby_exe("exit(0)")
+      -> {
+        $? >> 0
+      }.should complain(/warning: Process::Status#>> is deprecated and will be removed .*use other Process::Status attributes instead/)
+    end
+  end
 end
diff --git a/spec/ruby/core/range/reverse_each_spec.rb b/spec/ruby/core/range/reverse_each_spec.rb
index b80f9eef5bb2..b51e04c3fff2 100644
--- a/spec/ruby/core/range/reverse_each_spec.rb
+++ b/spec/ruby/core/range/reverse_each_spec.rb
@@ -2,7 +2,7 @@
 
 ruby_version_is "3.3" do
   describe "Range#reverse_each" do
-    it "traverses the Range in reverse order and pass each element to block" do
+    it "traverses the Range in reverse order and passes each element to block" do
       a = []
       (1..3).reverse_each { |i| a << i }
       a.should == [3, 2, 1]
@@ -88,8 +88,10 @@
           (1..3).reverse_each.size.should == 3
         end
 
-        it "returns Infinity when Range size is infinite" do
-          (..3).reverse_each.size.should == Float::INFINITY
+        ruby_bug "#20936", "3.4"..."3.5" do
+          it "returns Infinity when Range size is infinite" do
+            (..3).reverse_each.size.should == Float::INFINITY
+          end
         end
 
         it "returns nil when Range size is unknown" do
@@ -98,4 +100,4 @@
       end
     end
   end
-end
\ No newline at end of file
+end
diff --git a/spec/ruby/core/refinement/refined_class_spec.rb b/spec/ruby/core/refinement/refined_class_spec.rb
index 00b65d08955a..acc6e2cb2bfc 100644
--- a/spec/ruby/core/refinement/refined_class_spec.rb
+++ b/spec/ruby/core/refinement/refined_class_spec.rb
@@ -1,8 +1,29 @@
-require_relative '../../spec_helper'
+require_relative "../../spec_helper"
+require_relative 'shared/target'
 
 describe "Refinement#refined_class" do
   ruby_version_is "3.2"..."3.3" do
-    it "returns the class refined by the receiver" do
+    it_behaves_like :refinement_target, :refined_class
+  end
+
+  ruby_version_is "3.3"..."3.4" do
+    it "has been deprecated in favour of Refinement#target" do
+      refinement_int = nil
+
+      Module.new do
+        refine Integer do
+          refinement_int = self
+        end
+      end
+
+      -> {
+        refinement_int.refined_class
+      }.should complain(/warning: Refinement#refined_class is deprecated and will be removed in Ruby 3.4; use Refinement#target instead/)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "has been removed" do
       refinement_int = nil
 
       Module.new do
@@ -11,7 +32,7 @@
         end
       end
 
-      refinement_int.refined_class.should == Integer
+      refinement_int.should_not.respond_to?(:refined_class)
     end
   end
 end
diff --git a/spec/ruby/core/refinement/shared/target.rb b/spec/ruby/core/refinement/shared/target.rb
new file mode 100644
index 000000000000..79557bea0b96
--- /dev/null
+++ b/spec/ruby/core/refinement/shared/target.rb
@@ -0,0 +1,13 @@
+describe :refinement_target, shared: true do
+  it "returns the class refined by the receiver" do
+    refinement_int = nil
+
+    Module.new do
+      refine Integer do
+        refinement_int = self
+      end
+    end
+
+    refinement_int.send(@method).should == Integer
+  end
+end
diff --git a/spec/ruby/core/refinement/target_spec.rb b/spec/ruby/core/refinement/target_spec.rb
new file mode 100644
index 000000000000..fee9588a96ed
--- /dev/null
+++ b/spec/ruby/core/refinement/target_spec.rb
@@ -0,0 +1,8 @@
+require_relative "../../spec_helper"
+require_relative 'shared/target'
+
+describe "Refinement#target" do
+  ruby_version_is "3.3" do
+    it_behaves_like :refinement_target, :target
+  end
+end
diff --git a/spec/ruby/core/string/chilled_string_spec.rb b/spec/ruby/core/string/chilled_string_spec.rb
index 9f81b1af6d65..b8fb6eedc946 100644
--- a/spec/ruby/core/string/chilled_string_spec.rb
+++ b/spec/ruby/core/string/chilled_string_spec.rb
@@ -2,69 +2,141 @@
 
 describe "chilled String" do
   guard -> { ruby_version_is "3.4" and !"test".equal?("test") } do
-    describe "#frozen?" do
-      it "returns false" do
-        "chilled".frozen?.should == false
+    describe "chilled string literals" do
+
+      describe "#frozen?" do
+        it "returns false" do
+          "chilled".frozen?.should == false
+        end
       end
-    end
 
-    describe "#-@" do
-      it "returns a different instance" do
-        input = "chilled"
-        interned = (-input)
-        interned.frozen?.should == true
-        interned.object_id.should_not == input.object_id
+      describe "#-@" do
+        it "returns a different instance" do
+          input = "chilled"
+          interned = (-input)
+          interned.frozen?.should == true
+          interned.object_id.should_not == input.object_id
+        end
       end
-    end
 
-    describe "#+@" do
-      it "returns a different instance" do
-        input = "chilled"
-        duped = (+input)
-        duped.frozen?.should == false
-        duped.object_id.should_not == input.object_id
+      describe "#+@" do
+        it "returns a different instance" do
+          input = "chilled"
+          duped = (+input)
+          duped.frozen?.should == false
+          duped.object_id.should_not == input.object_id
+        end
       end
-    end
 
-    describe "#clone" do
-      it "preserves chilled status" do
-        input = "chilled".clone
-        -> {
-          input << "-mutated"
-        }.should complain(/literal string will be frozen in the future/)
-        input.should == "chilled-mutated"
+      describe "#clone" do
+        it "preserves chilled status" do
+          input = "chilled".clone
+          -> {
+            input << "-mutated"
+          }.should complain(/literal string will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+      end
+
+      describe "mutation" do
+        it "emits a warning" do
+          input = "chilled"
+          -> {
+            input << "-mutated"
+          }.should complain(/literal string will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+
+        it "emits a warning on singleton_class creation" do
+          -> {
+            "chilled".singleton_class
+          }.should complain(/literal string will be frozen in the future/)
+        end
+
+        it "emits a warning on instance variable assignment" do
+          -> {
+            "chilled".instance_variable_set(:@ivar, 42)
+          }.should complain(/literal string will be frozen in the future/)
+        end
+
+        it "raises FrozenError after the string was explicitly frozen" do
+          input = "chilled"
+          input.freeze
+          -> {
+            -> {
+            input << "mutated"
+            }.should raise_error(FrozenError)
+          }.should_not complain(/literal string will be frozen in the future/)
+        end
       end
     end
 
-    describe "mutation" do
-      it "emits a warning" do
-        input = "chilled"
-        -> {
-          input << "-mutated"
-        }.should complain(/literal string will be frozen in the future/)
-        input.should == "chilled-mutated"
+    describe "chilled strings returned by Symbol#to_s" do
+
+      describe "#frozen?" do
+        it "returns false" do
+          :chilled.to_s.frozen?.should == false
+        end
       end
 
-      it "emits a warning on singleton_class creation" do
-        -> {
-          "chilled".singleton_class
-        }.should complain(/literal string will be frozen in the future/)
+      describe "#-@" do
+        it "returns a different instance" do
+          input = :chilled.to_s
+          interned = (-input)
+          interned.frozen?.should == true
+          interned.object_id.should_not == input.object_id
+        end
       end
 
-      it "emits a warning on instance variable assignment" do
-        -> {
-          "chilled".instance_variable_set(:@ivar, 42)
-        }.should complain(/literal string will be frozen in the future/)
+      describe "#+@" do
+        it "returns a different instance" do
+          input = :chilled.to_s
+          duped = (+input)
+          duped.frozen?.should == false
+          duped.object_id.should_not == input.object_id
+        end
+      end
+
+      describe "#clone" do
+        it "preserves chilled status" do
+          input = :chilled.to_s.clone
+          -> {
+            input << "-mutated"
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
       end
 
-      it "raises FrozenError after the string was explicitly frozen" do
-        input = "chilled"
-        input.freeze
-        -> {
+      describe "mutation" do
+        it "emits a warning" do
+          input = :chilled.to_s
+          -> {
+            input << "-mutated"
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+
+        it "emits a warning on singleton_class creation" do
+          -> {
+            :chilled.to_s.singleton_class
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
+
+        it "emits a warning on instance variable assignment" do
+          -> {
+            :chilled.to_s.instance_variable_set(:@ivar, 42)
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
+
+        it "raises FrozenError after the string was explicitly frozen" do
+          input = :chilled.to_s
+          input.freeze
           -> {
-          input << "mutated"
-          }.should raise_error(FrozenError)
-        }.should_not complain(/literal string will be frozen in the future/)
+            -> {
+            input << "mutated"
+            }.should raise_error(FrozenError)
+          }.should_not complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
       end
     end
   end
diff --git a/spec/ruby/core/time/comparison_spec.rb b/spec/ruby/core/time/comparison_spec.rb
index 5b53c9fb50de..866fbea72ef1 100644
--- a/spec/ruby/core/time/comparison_spec.rb
+++ b/spec/ruby/core/time/comparison_spec.rb
@@ -55,6 +55,32 @@
     }.should_not complain
   end
 
+  context "given different timezones" do
+    it "returns 0 if time is the same as other" do
+      # three timezones, all at the same timestamp
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_cet = Time.new(2000, 1, 1, 1, 0, 0, '+01:00')
+      time_brt = Time.new(1999, 12, 31, 21, 0, 0, '-03:00')
+      (time_utc <=> time_cet).should == 0
+      (time_utc <=> time_brt).should == 0
+      (time_cet <=> time_brt).should == 0
+    end
+
+    it "returns -1 if the first argument is before the second argument" do
+      # time_brt is later, even though the date is earlier
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_brt = Time.new(1999, 12, 31, 23, 0, 0, '-03:00')
+      (time_utc <=> time_brt).should == -1
+    end
+
+    it "returns 1 if the first argument is before the second argument" do
+      # time_brt is later, even though the date is earlier
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_brt = Time.new(1999, 12, 31, 23, 0, 0, '-03:00')
+      (time_brt <=> time_utc).should == 1
+    end
+  end
+
   describe "given a non-Time argument" do
     it "returns nil if argument <=> self returns nil" do
       t = Time.now
diff --git a/spec/ruby/core/time/shared/gmtime.rb b/spec/ruby/core/time/shared/gmtime.rb
index bae19da4624d..7b4f65f0b796 100644
--- a/spec/ruby/core/time/shared/gmtime.rb
+++ b/spec/ruby/core/time/shared/gmtime.rb
@@ -4,7 +4,14 @@
     with_timezone("CST", -6) do
       t = Time.local(2007, 1, 9, 6, 0, 0)
       t.send(@method)
-      t.should == Time.gm(2007, 1, 9, 12, 0, 0)
+      # Time#== compensates for time zones, so check all parts separately
+      t.year.should == 2007
+      t.month.should == 1
+      t.mday.should == 9
+      t.hour.should == 12
+      t.min.should == 0
+      t.sec.should == 0
+      t.zone.should == "UTC"
     end
   end
 
diff --git a/spec/ruby/core/tracepoint/raised_exception_spec.rb b/spec/ruby/core/tracepoint/raised_exception_spec.rb
index ca2f50abb36f..5ac853184049 100644
--- a/spec/ruby/core/tracepoint/raised_exception_spec.rb
+++ b/spec/ruby/core/tracepoint/raised_exception_spec.rb
@@ -17,4 +17,22 @@
       raised_exception.should equal(error_result)
     end
   end
+
+  ruby_version_is "3.3" do
+    it 'returns value from exception rescued on the :rescue event' do
+      raised_exception, error_result = nil
+      trace = TracePoint.new(:rescue) { |tp|
+        next unless TracePointSpec.target_thread?
+        raised_exception = tp.raised_exception
+      }
+      trace.enable do
+        begin
+          raise StandardError
+        rescue => e
+          error_result = e
+        end
+        raised_exception.should equal(error_result)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/language/block_spec.rb b/spec/ruby/language/block_spec.rb
index a605a3619fdc..75c1e71bc2c0 100644
--- a/spec/ruby/language/block_spec.rb
+++ b/spec/ruby/language/block_spec.rb
@@ -999,6 +999,7 @@ def a; 1; end
   end
 end
 
+# tested more thoroughly in language/delegation_spec.rb
 describe "Anonymous block forwarding" do
   ruby_version_is "3.1" do
     it "forwards blocks to other method that formally declares anonymous block" do
diff --git a/spec/ruby/language/defined_spec.rb b/spec/ruby/language/defined_spec.rb
index 34408c019018..80ad1818b116 100644
--- a/spec/ruby/language/defined_spec.rb
+++ b/spec/ruby/language/defined_spec.rb
@@ -900,6 +900,10 @@
     defined?(DefinedSpecs::Undefined).should be_nil
   end
 
+  it "returns nil when the constant is not defined and the outer module implements .const_missing" do
+    defined?(DefinedSpecs::ModuleWithConstMissing::Undefined).should be_nil
+  end
+
   it "does not call .const_missing if the constant is not defined" do
     DefinedSpecs.should_not_receive(:const_missing)
     defined?(DefinedSpecs::UnknownChild).should be_nil
diff --git a/spec/ruby/language/delegation_spec.rb b/spec/ruby/language/delegation_spec.rb
index d780506421bd..b75f3f5f7cee 100644
--- a/spec/ruby/language/delegation_spec.rb
+++ b/spec/ruby/language/delegation_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../spec_helper'
 require_relative 'fixtures/delegation'
 
+# Forwarding anonymous parameters
 describe "delegation with def(...)" do
   it "delegates rest and kwargs" do
     a = Class.new(DelegationSpecs::Target)
@@ -10,10 +11,10 @@ def delegate(...)
       end
     RUBY
 
-    a.new.delegate(1, b: 2).should == [[1], {b: 2}]
+    a.new.delegate(1, b: 2).should == [[1], {b: 2}, nil]
   end
 
-  it "delegates block" do
+  it "delegates a block literal" do
     a = Class.new(DelegationSpecs::Target)
     a.class_eval(<<-RUBY)
       def delegate_block(...)
@@ -24,6 +25,18 @@ def delegate_block(...)
     a.new.delegate_block(1, b: 2) { |x| x }.should == [{b: 2}, [1]]
   end
 
+  it "delegates a block argument" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(...)
+        target(...)
+      end
+    RUBY
+
+    block = proc {}
+    a.new.delegate(1, b: 2, &block).should == [[1], {b: 2}, block]
+  end
+
   it "parses as open endless Range when brackets are omitted" do
     a = Class.new(DelegationSpecs::Target)
     suppress_warning do
@@ -34,7 +47,7 @@ def delegate(...)
       RUBY
     end
 
-    a.new.delegate(1, b: 2).should == Range.new([[], {}], nil, true)
+    a.new.delegate(1, b: 2).should == Range.new([[], {}, nil], nil, true)
   end
 end
 
@@ -47,10 +60,10 @@ def delegate(x, ...)
       end
     RUBY
 
-    a.new.delegate(0, 1, b: 2).should == [[1], {b: 2}]
+    a.new.delegate(0, 1, b: 2).should == [[1], {b: 2}, nil]
   end
 
-  it "delegates block" do
+  it "delegates a block literal" do
     a = Class.new(DelegationSpecs::Target)
     a.class_eval(<<-RUBY)
       def delegate_block(x, ...)
@@ -60,6 +73,18 @@ def delegate_block(x, ...)
 
     a.new.delegate_block(0, 1, b: 2) { |x| x }.should == [{b: 2}, [1]]
   end
+
+  it "delegates a block argument" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(...)
+        target(...)
+      end
+    RUBY
+
+    block = proc {}
+    a.new.delegate(1, b: 2, &block).should == [[1], {b: 2}, block]
+  end
 end
 
 ruby_version_is "3.2" do
@@ -70,9 +95,19 @@ def delegate_block(x, ...)
       def delegate(*)
         target(*)
       end
-    RUBY
+      RUBY
 
-      a.new.delegate(0, 1).should == [[0, 1], {}]
+      a.new.delegate(0, 1).should == [[0, 1], {}, nil]
+    end
+
+    ruby_version_is "3.3" do
+      context "within a block that accepts anonymous rest within a method that accepts anonymous rest" do
+        it "does not allow delegating rest" do
+          -> {
+            eval "def m(*); proc { |*| n(*) } end"
+          }.should raise_error(SyntaxError, /anonymous rest parameter is also used within block/)
+        end
+      end
     end
   end
 end
@@ -85,9 +120,45 @@ def delegate(*)
       def delegate(**)
         target(**)
       end
-    RUBY
+      RUBY
+
+      a.new.delegate(a: 1) { |x| x }.should == [[], {a: 1}, nil]
+    end
 
-      a.new.delegate(a: 1) { |x| x }.should == [[], {a: 1}]
+    ruby_version_is "3.3" do
+      context "within a block that accepts anonymous kwargs within a method that accepts anonymous kwargs" do
+        it "does not allow delegating kwargs" do
+          -> {
+            eval "def m(**); proc { |**| n(**) } end"
+          }.should raise_error(SyntaxError, /anonymous keyword rest parameter is also used within block/)
+        end
+      end
+    end
+  end
+end
+
+ruby_version_is "3.1" do
+  describe "delegation with def(&)" do
+    it "delegates an anonymous block parameter" do
+      a = Class.new(DelegationSpecs::Target)
+      a.class_eval(<<-RUBY)
+      def delegate(&)
+        target(&)
+      end
+      RUBY
+
+      block = proc {}
+      a.new.delegate(&block).should == [[], {}, block]
+    end
+
+    ruby_version_is "3.3" do
+      context "within a block that accepts anonymous block within a method that accepts anonymous block" do
+        it "does not allow delegating a block" do
+          -> {
+            eval "def m(&); proc { |&| n(&) } end"
+          }.should raise_error(SyntaxError, /anonymous block parameter is also used within block/)
+        end
+      end
     end
   end
 end
diff --git a/spec/ruby/language/fixtures/defined.rb b/spec/ruby/language/fixtures/defined.rb
index a9552619bf2a..3761cfa5bd40 100644
--- a/spec/ruby/language/fixtures/defined.rb
+++ b/spec/ruby/language/fixtures/defined.rb
@@ -285,6 +285,12 @@ def method_no_args
     end
   end
 
+  module ModuleWithConstMissing
+    def self.const_missing(const)
+      const
+    end
+  end
+
   class SuperWithIntermediateModules
     include IntermediateModule1
     include IntermediateModule2
diff --git a/spec/ruby/language/fixtures/delegation.rb b/spec/ruby/language/fixtures/delegation.rb
index 527d92839027..da2b02479197 100644
--- a/spec/ruby/language/fixtures/delegation.rb
+++ b/spec/ruby/language/fixtures/delegation.rb
@@ -1,7 +1,7 @@
 module DelegationSpecs
   class Target
-    def target(*args, **kwargs)
-      [args, kwargs]
+    def target(*args, **kwargs, &block)
+      [args, kwargs, block]
     end
 
     def target_block(*args, **kwargs)
diff --git a/spec/ruby/library/io-wait/wait_spec.rb b/spec/ruby/library/io-wait/wait_spec.rb
index 5952f127f757..61356ff395cc 100644
--- a/spec/ruby/library/io-wait/wait_spec.rb
+++ b/spec/ruby/library/io-wait/wait_spec.rb
@@ -91,14 +91,17 @@
       t.join # Thread#kill doesn't wait for the thread to end
     end
 
-    it "changes thread status to 'sleep' when waits for WRITABLE event" do
-      IOSpec.exhaust_write_buffer(@w)
-
-      t = Thread.new { @w.wait(IO::WRITABLE, 10) }
-      sleep 1
-      t.status.should == 'sleep'
-      t.kill
-      t.join # Thread#kill doesn't wait for the thread to end
+    # https://github.com/ruby/ruby/actions/runs/11948300522/job/33305664284?pr=12139
+    platform_is_not :windows do
+      it "changes thread status to 'sleep' when waits for WRITABLE event" do
+        IOSpec.exhaust_write_buffer(@w)
+
+        t = Thread.new { @w.wait(IO::WRITABLE, 10) }
+        sleep 1
+        t.status.should == 'sleep'
+        t.kill
+        t.join # Thread#kill doesn't wait for the thread to end
+      end
     end
 
     it "can be interrupted when waiting for READABLE event" do
diff --git a/spec/ruby/library/random/formatter/alphanumeric_spec.rb b/spec/ruby/library/random/formatter/alphanumeric_spec.rb
new file mode 100644
index 000000000000..df14c29e2454
--- /dev/null
+++ b/spec/ruby/library/random/formatter/alphanumeric_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.1" do
+  require 'random/formatter'
+
+  describe "Random::Formatter#alphanumeric" do
+    before :each do
+      @object = Object.new
+      @object.extend(Random::Formatter)
+      @object.define_singleton_method(:bytes) do |n|
+        "\x00".b * n
+      end
+    end
+
+    it "generates a random alphanumeric string" do
+      @object.alphanumeric.should =~ /\A[A-Za-z0-9]+\z/
+    end
+
+    it "has a default size of 16 characters" do
+      @object.alphanumeric.size.should == 16
+    end
+
+    it "accepts a 'size' argument" do
+      @object.alphanumeric(10).size.should == 10
+    end
+
+    it "uses the default size if 'nil' is given as size argument" do
+      @object.alphanumeric(nil).size.should == 16
+    end
+
+    it "raises an ArgumentError if the size is not numeric" do
+      -> {
+        @object.alphanumeric("10")
+      }.should raise_error(ArgumentError)
+    end
+
+    it "does not coerce the size argument with #to_int" do
+      size = mock("size")
+      size.should_not_receive(:to_int)
+      -> {
+        @object.alphanumeric(size)
+      }.should raise_error(ArgumentError)
+    end
+
+    ruby_version_is "3.3" do
+      it "accepts a 'chars' argument with the output alphabet" do
+        @object.alphanumeric(chars: ['a', 'b']).should =~ /\A[ab]+\z/
+      end
+
+      it "converts the elements of chars using #to_s" do
+        to_s = mock("to_s")
+        to_s.should_receive(:to_s).and_return("[mock to_s]")
+        # Using 1 value in chars results in an infinite loop
+        @object.alphanumeric(1, chars: [to_s, to_s]).should == "[mock to_s]"
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/securerandom/random_number_spec.rb b/spec/ruby/library/securerandom/random_number_spec.rb
index 03781f49019c..bb25bc496ed9 100644
--- a/spec/ruby/library/securerandom/random_number_spec.rb
+++ b/spec/ruby/library/securerandom/random_number_spec.rb
@@ -11,8 +11,8 @@
     (1..64).each do |idx|
       num = SecureRandom.random_number(idx)
       num.should be_kind_of(Integer)
-      (0 <= num).should == true
-      (num < idx).should == true
+      0.should <= num
+      num.should < idx
     end
   end
 
@@ -21,8 +21,8 @@
     11.times do
       num = SecureRandom.random_number max
       num.should be_kind_of(Integer)
-      (0 <= num).should == true
-      (num < max).should == true
+      0.should <= num
+      num.should < max
     end
   end
 
@@ -30,8 +30,8 @@
     64.times do
       num = SecureRandom.random_number
       num.should be_kind_of(Float)
-      (0.0 <= num).should == true
-      (num < 1.0).should == true
+      0.0.should <= num
+      num.should < 1.0
     end
   end
 
@@ -39,8 +39,8 @@
     64.times do
       num = SecureRandom.random_number 11...13
       num.should be_kind_of(Integer)
-      (11 <= num).should == true
-      (num < 13).should == true
+      11.should <= num
+      num.should < 13
     end
   end
 
@@ -50,8 +50,8 @@
     32.times do
       num = SecureRandom.random_number lower..upper
       num.should be_kind_of(Integer)
-      (lower <= num).should == true
-      (num <= upper).should == true
+      lower.should <= num
+      num.should <= upper
     end
   end
 
@@ -59,23 +59,23 @@
     64.times do
       num = SecureRandom.random_number 0.6..0.9
       num.should be_kind_of(Float)
-      (0.6 <= num).should == true
-      (num <= 0.9).should == true
+      0.6.should <= num
+      num.should <= 0.9
     end
   end
 
   it "generates a random float number between 0.0 and 1.0 if argument is negative" do
     num = SecureRandom.random_number(-10)
     num.should be_kind_of(Float)
-    (0.0 <= num).should == true
-    (num < 1.0).should == true
+    0.0.should <= num
+    num.should < 1.0
   end
 
   it "generates a random float number between 0.0 and 1.0 if argument is negative float" do
     num = SecureRandom.random_number(-11.1)
     num.should be_kind_of(Float)
-    (0.0 <= num).should == true
-    (num < 1.0).should == true
+    0.0.should <= num
+    num.should < 1.0
   end
 
   it "generates different float numbers with subsequent invocations" do
@@ -84,7 +84,7 @@
     256.times do
       val = SecureRandom.random_number
       # make sure the random values are not repeating
-      values.include?(val).should == false
+      values.should_not include(val)
       values << val
     end
   end
diff --git a/spec/ruby/library/socket/socket/connect_spec.rb b/spec/ruby/library/socket/socket/connect_spec.rb
index 175c9942bcd6..7fceb47b009f 100644
--- a/spec/ruby/library/socket/socket/connect_spec.rb
+++ b/spec/ruby/library/socket/socket/connect_spec.rb
@@ -63,7 +63,11 @@
       client.timeout = 0
 
       -> {
-        client.connect(address)
+        begin
+          client.connect(address)
+        rescue Errno::ECONNREFUSED
+          skip "Outgoing packets may be filtered"
+        end
       }.should raise_error(IO::TimeoutError)
     end
   end
diff --git a/spec/ruby/optional/capi/ext/hash_spec.c b/spec/ruby/optional/capi/ext/hash_spec.c
index e7fdbb10f474..0e5b3d1c0aa6 100644
--- a/spec/ruby/optional/capi/ext/hash_spec.c
+++ b/spec/ruby/optional/capi/ext/hash_spec.c
@@ -136,7 +136,7 @@ VALUE hash_spec_compute_a_hash_code(VALUE self, VALUE seed) {
 
 VALUE hash_spec_rb_hash_bulk_insert(VALUE self, VALUE array_len, VALUE array, VALUE hash) {
   VALUE* ptr;
-  
+
   if (array == Qnil) {
     ptr = NULL;
   } else {
diff --git a/spec/ruby/optional/capi/io_spec.rb b/spec/ruby/optional/capi/io_spec.rb
index a34b3a4ff051..dbfaf556f6a7 100644
--- a/spec/ruby/optional/capi/io_spec.rb
+++ b/spec/ruby/optional/capi/io_spec.rb
@@ -531,123 +531,135 @@
       end
     end
 
-    describe "rb_io_open_descriptor" do
-      it "creates a new IO instance" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.should.is_a?(IO)
-      end
+    quarantine! do # "Errno::EBADF: Bad file descriptor" at closing @r_io, @rw_io etc in the after :each hook
+      describe "rb_io_open_descriptor" do
+        it "creates a new IO instance" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.is_a?(IO)
+        end
 
-      it "return an instance of the specified class" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.class.should == File
+        it "return an instance of the specified class" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.class.should == File
 
-        io = @o.rb_io_open_descriptor(IO, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.class.should == IO
-      end
+          io = @o.rb_io_open_descriptor(IO, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.class.should == IO
+        end
 
-      it "sets the specified file descriptor" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.fileno.should == @r_io.fileno
-      end
+        it "sets the specified file descriptor" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.fileno.should == @r_io.fileno
+        end
 
-      it "sets the specified path" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.path.should == "a.txt"
-      end
+        it "sets the specified path" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should == "a.txt"
+        end
 
-      it "sets the specified mode" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_BINMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.should.binmode?
+        it "sets the specified mode" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_BINMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.binmode?
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_TEXTMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.should_not.binmode?
-      end
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_TEXTMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should_not.binmode?
+        end
 
-      it "sets the specified timeout" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.timeout.should == 60
-      end
+        it "sets the specified timeout" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.timeout.should == 60
+        end
 
-      it "sets the specified internal encoding" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.internal_encoding.should == Encoding::US_ASCII
-      end
+        it "sets the specified internal encoding" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.internal_encoding.should == Encoding::US_ASCII
+        end
 
-      it "sets the specified external encoding" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.external_encoding.should == Encoding::UTF_8
-      end
+        it "sets the specified external encoding" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.external_encoding.should == Encoding::UTF_8
+        end
 
-      it "does not apply the specified encoding flags" do
-        File.write("a.txt", "123\r\n456\n89")
-        file = File.open("a.txt", "r")
+        it "does not apply the specified encoding flags" do
+          name = tmp("rb_io_open_descriptor_specs")
+          File.write(name, "123\r\n456\n89")
+          file = File.open(name, "r")
 
-        io = @o.rb_io_open_descriptor(File, file.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", CApiIOSpecs::ECONV_UNIVERSAL_NEWLINE_DECORATOR, {})
-        io.read_nonblock(20).should == "123\r\n456\n89"
-      end
+          io = @o.rb_io_open_descriptor(File, file.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", CApiIOSpecs::ECONV_UNIVERSAL_NEWLINE_DECORATOR, {})
+          io.read_nonblock(20).should == "123\r\n456\n89"
+        ensure
+          file.close
+          rm_r name
+        end
 
-      it "ignores the IO open options" do
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {external_encoding: "windows-1251"})
-        io.external_encoding.should == Encoding::UTF_8
+        it "ignores the IO open options" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {external_encoding: "windows-1251"})
+          io.external_encoding.should == Encoding::UTF_8
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {internal_encoding: "windows-1251"})
-        io.internal_encoding.should == Encoding::US_ASCII
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {internal_encoding: "windows-1251"})
+          io.internal_encoding.should == Encoding::US_ASCII
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {encoding: "windows-1251:binary"})
-        io.external_encoding.should == Encoding::UTF_8
-        io.internal_encoding.should == Encoding::US_ASCII
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {encoding: "windows-1251:binary"})
+          io.external_encoding.should == Encoding::UTF_8
+          io.internal_encoding.should == Encoding::US_ASCII
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {textmode: false})
-        io.should_not.binmode?
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {textmode: false})
+          io.should_not.binmode?
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {binmode: true})
-        io.should_not.binmode?
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {binmode: true})
+          io.should_not.binmode?
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {autoclose: false})
-        io.should.autoclose?
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {autoclose: false})
+          io.should.autoclose?
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {path: "a.txt"})
-        io.path.should == "a.txt"
-      end
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {path: "a.txt"})
+          io.path.should == "a.txt"
+        end
 
-      it "ignores the IO encoding options" do
-        io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_WRITABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {crlf_newline: true})
+        it "ignores the IO encoding options" do
+          io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_WRITABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {crlf_newline: true})
 
-        io.write("123\r\n456\n89")
-        io.flush
+          io.write("123\r\n456\n89")
+          io.flush
 
-        @r_io.read_nonblock(20).should == "123\r\n456\n89"
-      end
+          @r_io.read_nonblock(20).should == "123\r\n456\n89"
+        end
 
-      it "allows wrong mode" do
-        io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
-        io.should.is_a?(File)
+        it "allows wrong mode" do
+          io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.is_a?(File)
 
-        -> { io.read_nonblock(1) }.should raise_error(Errno::EBADF)
-      end
+          platform_is_not :windows do
+            -> { io.read_nonblock(1) }.should raise_error(Errno::EBADF)
+          end
 
-      it "tolerates NULL as rb_io_encoding *encoding parameter" do
-        io = @o.rb_io_open_descriptor_without_encoding(File, @r_io.fileno, 0, "a.txt", 60)
-        io.should.is_a?(File)
-      end
+          platform_is :windows do
+            -> { io.read_nonblock(1) }.should raise_error(IO::EWOULDBLOCKWaitReadable)
+          end
+        end
+
+        it "tolerates NULL as rb_io_encoding *encoding parameter" do
+          io = @o.rb_io_open_descriptor_without_encoding(File, @r_io.fileno, 0, "a.txt", 60)
+          io.should.is_a?(File)
+        end
 
-      it "deduplicates path String" do
-        path = "a.txt".dup
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
-        io.path.should_not equal(path)
+        it "deduplicates path String" do
+          path = "a.txt".dup
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should_not equal(path)
 
-        path = "a.txt".freeze
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
-        io.path.should_not equal(path)
-      end
+          path = "a.txt".freeze
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should_not equal(path)
+        end
 
-      it "calls #to_str to convert a path to a String" do
-        path = Object.new
-        def path.to_str; "a.txt"; end
+        it "calls #to_str to convert a path to a String" do
+          path = Object.new
+          def path.to_str; "a.txt"; end
 
-        io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
 
-        io.path.should == "a.txt"
+          io.path.should == "a.txt"
+        end
       end
     end
   end
diff --git a/spec/ruby/optional/capi/kernel_spec.rb b/spec/ruby/optional/capi/kernel_spec.rb
index 96d61ee003c4..c90e50f1db9c 100644
--- a/spec/ruby/optional/capi/kernel_spec.rb
+++ b/spec/ruby/optional/capi/kernel_spec.rb
@@ -197,9 +197,13 @@ class CApiKernelSpecs::Exc < StandardError
     end
 
     it "uses an 'unknown error' message when errno is unknown" do
-      -> do
-        @s.rb_syserr_fail(-10, nil)
-      end.should raise_error(SystemCallError, /Unknown error(:)? -1/) # a new class Errno::E-01 is generated on the fly
+      platform_is_not :windows do
+        -> { @s.rb_syserr_fail(-10, nil) }.should raise_error(SystemCallError, /Unknown error(:)? -10/)
+      end
+
+      platform_is :windows do
+        -> { @s.rb_syserr_fail(-1, nil) }.should raise_error(SystemCallError, "The operation completed successfully.")
+      end
     end
   end
 
@@ -217,9 +221,13 @@ class CApiKernelSpecs::Exc < StandardError
     end
 
     it "uses an 'unknown error' message when errno is unknown" do
-      -> do
-        @s.rb_syserr_fail_str(-1, nil)
-      end.should raise_error(SystemCallError, /Unknown error(:)? -1/) # a new class Errno::E-01 is generated on the fly
+      platform_is_not :windows do
+        -> { @s.rb_syserr_fail_str(-10, nil) }.should raise_error(SystemCallError, /Unknown error(:)? -10/)
+      end
+
+      platform_is :windows do
+        -> { @s.rb_syserr_fail_str(-1, nil) }.should raise_error(SystemCallError, "The operation completed successfully.")
+      end
     end
   end
 
diff --git a/spec/ruby/shared/process/fork.rb b/spec/ruby/shared/process/fork.rb
index 11e18d7b1cef..8dbb3d0da43d 100644
--- a/spec/ruby/shared/process/fork.rb
+++ b/spec/ruby/shared/process/fork.rb
@@ -23,31 +23,31 @@
     end
 
     it "returns status zero" do
-      pid = Process.fork { exit! 0 }
+      pid = @object.fork { exit! 0 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status zero" do
-      pid = Process.fork { exit 0 }
+      pid = @object.fork { exit 0 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status zero" do
-      pid = Process.fork {}
+      pid = @object.fork {}
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status non-zero" do
-      pid = Process.fork { exit! 42 }
+      pid = @object.fork { exit! 42 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 42
     end
 
     it "returns status non-zero" do
-      pid = Process.fork { exit 42 }
+      pid = @object.fork { exit 42 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 42
     end
diff --git a/spec/ruby/shared/rational/exponent.rb b/spec/ruby/shared/rational/exponent.rb
index b0e9b2357416..2145d6baceae 100644
--- a/spec/ruby/shared/rational/exponent.rb
+++ b/spec/ruby/shared/rational/exponent.rb
@@ -84,47 +84,91 @@
       (Rational(-1) ** bignum_value(3)).should eql(Rational(-1))
     end
 
-    it "returns positive Infinity when self is > 1" do
-      -> {
-        (Rational(2) ** bignum_value).infinite?.should == 1
-      }.should complain(/warning: in a\*\*b, b may be too big/)
-      -> {
-        (Rational(fixnum_max) ** bignum_value).infinite?.should == 1
-      }.should complain(/warning: in a\*\*b, b may be too big/)
-    end
-
-    it "returns 0.0 when self is > 1 and the exponent is negative" do
-      -> {
-        (Rational(2) ** -bignum_value).should eql(0.0)
-      }.should complain(/warning: in a\*\*b, b may be too big/)
-      -> {
-        (Rational(fixnum_max) ** -bignum_value).should eql(0.0)
-      }.should complain(/warning: in a\*\*b, b may be too big/)
-    end
-
-    # Fails on linux due to pow() bugs in glibc: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866
-    platform_is_not :linux do
-      it "returns positive Infinity when self < -1" do
+    ruby_version_is ""..."3.4" do
+      it "returns positive Infinity when self is > 1" do
         -> {
-          (Rational(-2) ** bignum_value).infinite?.should == 1
+          (Rational(2) ** bignum_value).infinite?.should == 1
         }.should complain(/warning: in a\*\*b, b may be too big/)
         -> {
-          (Rational(-2) ** (bignum_value + 1)).infinite?.should == 1
-        }.should complain(/warning: in a\*\*b, b may be too big/)
-        -> {
-          (Rational(fixnum_min) ** bignum_value).infinite?.should == 1
+          (Rational(fixnum_max) ** bignum_value).infinite?.should == 1
         }.should complain(/warning: in a\*\*b, b may be too big/)
       end
 
-      it "returns 0.0 when self is < -1 and the exponent is negative" do
+      it "returns 0.0 when self is > 1 and the exponent is negative" do
         -> {
-          (Rational(-2) ** -bignum_value).should eql(0.0)
+          (Rational(2) ** -bignum_value).should eql(0.0)
         }.should complain(/warning: in a\*\*b, b may be too big/)
         -> {
-          (Rational(fixnum_min) ** -bignum_value).should eql(0.0)
+          (Rational(fixnum_max) ** -bignum_value).should eql(0.0)
         }.should complain(/warning: in a\*\*b, b may be too big/)
       end
     end
+
+    ruby_version_is "3.4" do
+      it "raises an ArgumentError when self is > 1" do
+        -> {
+          (Rational(2) ** bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_max) ** bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+
+      it "raises an ArgumentError when self is > 1 and the exponent is negative" do
+        -> {
+          (Rational(2) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_max) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+    end
+
+    # Fails on linux due to pow() bugs in glibc: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866
+    platform_is_not :linux do
+      ruby_version_is ""..."3.4" do
+        it "returns positive Infinity when self < -1" do
+          -> {
+            (Rational(-2) ** bignum_value).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(-2) ** (bignum_value + 1)).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(fixnum_min) ** bignum_value).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+        end
+
+        it "returns 0.0 when self is < -1 and the exponent is negative" do
+          -> {
+            (Rational(-2) ** -bignum_value).should eql(0.0)
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(fixnum_min) ** -bignum_value).should eql(0.0)
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "returns positive Infinity when self < -1" do
+          -> {
+            (Rational(-2) ** bignum_value)
+          }.should raise_error(ArgumentError)
+          -> {
+            (Rational(fixnum_min) ** bignum_value)
+          }.should raise_error(ArgumentError)
+        end
+
+        it "returns 0.0 when self is < -1 and the exponent is negative" do
+          -> {
+            (Rational(-2) ** -bignum_value)
+          }.should raise_error(ArgumentError)
+          -> {
+            (Rational(fixnum_min) ** -bignum_value)
+          }.should raise_error(ArgumentError)
+        end
+      end
+    end
   end
 
   describe "when passed Float" do
diff --git a/spec/tags/core/module/deprecate_constant_tags.txt b/spec/tags/core/module/deprecate_constant_tags.txt
new file mode 100644
index 000000000000..d165b14f15ef
--- /dev/null
+++ b/spec/tags/core/module/deprecate_constant_tags.txt
@@ -0,0 +1 @@
+fails:Module#deprecate_constant when removing the deprecated module warns with a message
diff --git a/spec/tags/core/process/status/bit_and_tags.txt b/spec/tags/core/process/status/bit_and_tags.txt
new file mode 100644
index 000000000000..d882c7260d62
--- /dev/null
+++ b/spec/tags/core/process/status/bit_and_tags.txt
@@ -0,0 +1,6 @@
+slow:Process::Status#& returns a bitwise and of the integer status of an exited child
+slow:Process::Status#& raises an ArgumentError if mask is negative
+slow:Process::Status#& shows a deprecation warning
+fails:Process::Status#& returns a bitwise and of the integer status of an exited child
+fails:Process::Status#& raises an ArgumentError if mask is negative
+fails:Process::Status#& shows a deprecation warning
diff --git a/spec/tags/core/process/status/right_shift_tags.txt b/spec/tags/core/process/status/right_shift_tags.txt
new file mode 100644
index 000000000000..57fb6489236c
--- /dev/null
+++ b/spec/tags/core/process/status/right_shift_tags.txt
@@ -0,0 +1,5 @@
+slow:Process::Status#>> returns a right shift of the integer status of an exited child
+slow:Process::Status#>> raises an ArgumentError if shift value is negative
+slow:Process::Status#>> shows a deprecation warning
+fails:Process::Status#>> raises an ArgumentError if shift value is negative
+fails:Process::Status#>> shows a deprecation warning
diff --git a/spec/tags/core/refinement/refined_class_tags.txt b/spec/tags/core/refinement/refined_class_tags.txt
new file mode 100644
index 000000000000..117517584109
--- /dev/null
+++ b/spec/tags/core/refinement/refined_class_tags.txt
@@ -0,0 +1 @@
+fails:Refinement#refined_class has been deprecated in favour of Refinement#target
diff --git a/spec/tags/core/refinement/target_tags.txt b/spec/tags/core/refinement/target_tags.txt
new file mode 100644
index 000000000000..09b279765c95
--- /dev/null
+++ b/spec/tags/core/refinement/target_tags.txt
@@ -0,0 +1 @@
+fails:Refinement#target returns the class refined by the receiver
diff --git a/spec/tags/core/tracepoint/raised_exception_tags.txt b/spec/tags/core/tracepoint/raised_exception_tags.txt
index 3a32ffe6c5b1..d3fd91512314 100644
--- a/spec/tags/core/tracepoint/raised_exception_tags.txt
+++ b/spec/tags/core/tracepoint/raised_exception_tags.txt
@@ -1 +1,2 @@
 fails:TracePoint#raised_exception returns value from exception raised on the :raise event
+fails:TracePoint#raised_exception returns value from exception rescued on the :rescue event