Update to ruby/spec@9d69b95

99 files changed, 1704 insertions, 202 deletions

diff --git a/spec/ruby/core/array/keep_if_spec.rb b/spec/ruby/core/array/keep_if_spec.rb
index bf2bdeaf91..40f7329b7c 100644
--- a/spec/ruby/core/array/keep_if_spec.rb
+++ b/spec/ruby/core/array/keep_if_spec.rb
@@ -1,3 +1,4 @@
+require_relative '../../spec_helper'
 require_relative 'shared/keep_if'
 
 describe "Array#keep_if" do
diff --git a/spec/ruby/core/array/pack/c_spec.rb b/spec/ruby/core/array/pack/c_spec.rb
index 7200830331..be03551629 100644
--- a/spec/ruby/core/array/pack/c_spec.rb
+++ b/spec/ruby/core/array/pack/c_spec.rb
@@ -45,8 +45,18 @@ describe :array_pack_8bit, shared: true do
     [1, 2, 3, 4, 5].pack(pack_format('*')).should == "\x01\x02\x03\x04\x05"
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack(pack_format("\000", 2)).should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [1, 2, 3].pack(pack_format("\000", 2)).should == "\x01\x02"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/shared/basic.rb b/spec/ruby/core/array/pack/shared/basic.rb
index 23e239d3de..65fdaa45d8 100644
--- a/spec/ruby/core/array/pack/shared/basic.rb
+++ b/spec/ruby/core/array/pack/shared/basic.rb
@@ -27,6 +27,42 @@ describe :array_pack_basic_non_float, shared: true do
     [@obj, @obj].pack("a \t\n\v\f\r"+pack_format).should be_an_instance_of(String)
   end
 
+  it "ignores comments in the format string" do
+    # 2 additional directives ('a') are required for the X directive
+    [@obj, @obj, @obj, @obj].pack("aa #{pack_format} # some comment \n#{pack_format}").should be_an_instance_of(String)
+  end
+  
+  ruby_version_is ""..."3.2" do
+    it "warns in verbose mode that a directive is unknown" do
+      # additional directive ('a') is required for the X directive
+      -> { [@obj, @obj].pack("a R" + pack_format) }.should complain(/unknown pack directive 'R'/, verbose: true)
+      -> { [@obj, @obj].pack("a 0" + pack_format) }.should complain(/unknown pack directive '0'/, verbose: true)
+      -> { [@obj, @obj].pack("a :" + pack_format) }.should complain(/unknown pack directive ':'/, verbose: true)
+    end
+  end
+
+  ruby_version_is "3.2"..."3.3" do
+    # https://bugs.ruby-lang.org/issues/19150
+    # NOTE: it's just a plan of the Ruby core team
+    it "warns that a directive is unknown" do
+      # additional directive ('a') is required for the X directive
+      -> { [@obj, @obj].pack("a R" + pack_format) }.should complain(/unknown pack directive 'R'/)
+      -> { [@obj, @obj].pack("a 0" + pack_format) }.should complain(/unknown pack directive '0'/)
+      -> { [@obj, @obj].pack("a :" + pack_format) }.should complain(/unknown pack directive ':'/)
+    end
+  end
+
+  ruby_version_is "3.3" do
+    # https://bugs.ruby-lang.org/issues/19150
+    # NOTE: Added this case just to not forget about the decision in the ticket
+    it "raise ArgumentError when a directive is unknown" do
+      # additional directive ('a') is required for the X directive
+      -> { [@obj, @obj].pack("a R" + pack_format) }.should raise_error(ArgumentError)
+      -> { [@obj, @obj].pack("a 0" + pack_format) }.should raise_error(ArgumentError)
+      -> { [@obj, @obj].pack("a :" + pack_format) }.should raise_error(ArgumentError)
+    end
+  end
+
   it "calls #to_str to coerce the directives string" do
     d = mock("pack directive")
     d.should_receive(:to_str).and_return("x"+pack_format)
@@ -39,6 +75,10 @@ describe :array_pack_basic_float, shared: true do
     [9.3, 4.7].pack(" \t\n\v\f\r"+pack_format).should be_an_instance_of(String)
   end
 
+  it "ignores comments in the format string" do
+    [9.3, 4.7].pack(pack_format + "# some comment \n" + pack_format).should be_an_instance_of(String)
+  end
+
   it "calls #to_str to coerce the directives string" do
     d = mock("pack directive")
     d.should_receive(:to_str).and_return("x"+pack_format)
diff --git a/spec/ruby/core/array/pack/shared/float.rb b/spec/ruby/core/array/pack/shared/float.rb
index ba174a071a..9510cffed7 100644
--- a/spec/ruby/core/array/pack/shared/float.rb
+++ b/spec/ruby/core/array/pack/shared/float.rb
@@ -25,8 +25,18 @@ describe :array_pack_float_le, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "\x9a\x999@33\xb3?33\x03A"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "\x9a\x99\xa9@33\x13A"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [5.3, 9.2].pack(pack_format("\000", 2)).should == "\x9a\x99\xa9@33\x13A"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -74,6 +84,11 @@ describe :array_pack_float_be, shared: true do
 
   it "converts an Integer to a Float" do
     [8].pack(pack_format).should == "A\x00\x00\x00"
+    [bignum_value].pack(pack_format).should == "_\x80\x00\x00"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "A\x00\x00\x00"
   end
 
   it "raises a TypeError if passed a String representation of a floating point number" do
@@ -88,8 +103,18 @@ describe :array_pack_float_be, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@9\x99\x9a?\xb333A\x0333"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\xa9\x99\x9aA\x1333"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\xa9\x99\x9aA\x1333"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -129,6 +154,11 @@ describe :array_pack_double_le, shared: true do
 
   it "converts an Integer to a Float" do
     [8].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\x20@"
+    [bignum_value].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\xF0C"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00 @"
   end
 
   it "raises a TypeError if passed a String representation of a floating point number" do
@@ -143,8 +173,18 @@ describe :array_pack_double_le, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "333333\x07@ffffff\xf6?ffffff\x20@"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "333333\x15@ffffff\x22@"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [5.3, 9.2].pack(pack_format("\000", 2)).should == "333333\x15@ffffff\x22@"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -202,8 +242,18 @@ describe :array_pack_double_be, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@\x07333333?\xf6ffffff@\x20ffffff"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\x15333333@\x22ffffff"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\x15333333@\x22ffffff"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/shared/integer.rb b/spec/ruby/core/array/pack/shared/integer.rb
index 6592f85022..d3ce9b5792 100644
--- a/spec/ruby/core/array/pack/shared/integer.rb
+++ b/spec/ruby/core/array/pack/shared/integer.rb
@@ -41,9 +41,19 @@ describe :array_pack_16bit_le, shared: true do
     str.should == "\x78\x65\xcd\xab\x21\x43"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x78\x65\xcd\xab"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      str.should == "\x78\x65\xcd\xab"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -93,9 +103,19 @@ describe :array_pack_16bit_be, shared: true do
     str.should == "\x65\x78\xab\xcd\x43\x21"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x65\x78\xab\xcd"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      str.should == "\x65\x78\xab\xcd"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -145,9 +165,19 @@ describe :array_pack_32bit_le, shared: true do
     str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde\x21\x43\x65\x78"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -197,9 +227,19 @@ describe :array_pack_32bit_be, shared: true do
     str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd\x78\x65\x43\x21"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -309,9 +349,19 @@ describe :array_pack_64bit_le, shared: true do
     str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
-    str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -369,9 +419,19 @@ describe :array_pack_64bit_be, shared: true do
     str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
-    str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/shared/numeric_basic.rb b/spec/ruby/core/array/pack/shared/numeric_basic.rb
index 7c36ba4a32..545e215e64 100644
--- a/spec/ruby/core/array/pack/shared/numeric_basic.rb
+++ b/spec/ruby/core/array/pack/shared/numeric_basic.rb
@@ -37,8 +37,14 @@ describe :array_pack_float, shared: true do
     -> { ["a"].pack(pack_format) }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError when the object does not respond to #to_f" do
-    obj = mock('not an float')
+  it "raises a TypeError when the object is not Numeric" do
+    obj = Object.new
+    -> { [obj].pack(pack_format) }.should raise_error(TypeError, /can't convert Object into Float/)
+  end
+
+  it "raises a TypeError when the Numeric object does not respond to #to_f" do
+    klass = Class.new(Numeric)
+    obj = klass.new
     -> { [obj].pack(pack_format) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/array/pack/shared/unicode.rb b/spec/ruby/core/array/pack/shared/unicode.rb
index dd0f8b38aa..130c447bb7 100644
--- a/spec/ruby/core/array/pack/shared/unicode.rb
+++ b/spec/ruby/core/array/pack/shared/unicode.rb
@@ -67,8 +67,18 @@ describe :array_pack_unicode, shared: true do
     -> { [obj].pack("U") }.should raise_error(TypeError)
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack("U\x00U").should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [1, 2, 3].pack("U\x00U").should == "\x01\x02"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack("U\x00U")
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/w_spec.rb b/spec/ruby/core/array/pack/w_spec.rb
index 439fa02198..e241d1519c 100644
--- a/spec/ruby/core/array/pack/w_spec.rb
+++ b/spec/ruby/core/array/pack/w_spec.rb
@@ -24,8 +24,18 @@ describe "Array#pack with format 'w'" do
     [obj].pack("w").should == "\x05"
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack("w\x00w").should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      [1, 2, 3].pack("w\x00w").should == "\x01\x02"
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack("w\x00w")
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/shared/unshift.rb b/spec/ruby/core/array/shared/unshift.rb
index fc82e19e2a..4941e098f6 100644
--- a/spec/ruby/core/array/shared/unshift.rb
+++ b/spec/ruby/core/array/shared/unshift.rb
@@ -22,6 +22,11 @@ describe :array_unshift, shared: true do
     a.should == [3, 4]
   end
 
+  it "returns self" do
+    a = [1, 2, 3]
+    a.send(@method, "a").should.equal?(a)
+  end
+
   it "quietly ignores unshifting nothing" do
     [].send(@method).should == []
   end
@@ -43,4 +48,17 @@ describe :array_unshift, shared: true do
   it "raises a FrozenError on a frozen array when the array would not be modified" do
     -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(FrozenError)
   end
+
+  # https://github.com/oracle/truffleruby/issues/2772
+  it "doesn't rely on Array#[]= so it can be overridden" do
+    subclass = Class.new(Array) do
+      def []=(*)
+        raise "[]= is called"
+      end
+    end
+
+    array = subclass.new
+    array.send(@method, 1)
+    array.should == [1]
+  end
 end
diff --git a/spec/ruby/core/array/values_at_spec.rb b/spec/ruby/core/array/values_at_spec.rb
index 2c6fd16947..e85bbee400 100644
--- a/spec/ruby/core/array/values_at_spec.rb
+++ b/spec/ruby/core/array/values_at_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+# Should be synchronized with core/struct/values_at_spec.rb
 describe "Array#values_at" do
   it "returns an array of elements at the indexes when passed indexes" do
     [1, 2, 3, 4, 5].values_at().should == []
diff --git a/spec/ruby/core/array/zip_spec.rb b/spec/ruby/core/array/zip_spec.rb
index af4013debe..2a0f64cb49 100644
--- a/spec/ruby/core/array/zip_spec.rb
+++ b/spec/ruby/core/array/zip_spec.rb
@@ -62,4 +62,10 @@ describe "Array#zip" do
   it "does not return subclass instance on Array subclasses" do
     ArraySpecs::MyArray[1, 2, 3].zip(["a", "b"]).should be_an_instance_of(Array)
   end
+
+  it "raises TypeError when some argument isn't Array and doesn't respond to #to_ary and #to_enum" do
+    -> { [1, 2, 3].zip(Object.new) }.should raise_error(TypeError, "wrong argument type Object (must respond to :each)")
+    -> { [1, 2, 3].zip(1) }.should raise_error(TypeError, "wrong argument type Integer (must respond to :each)")
+    -> { [1, 2, 3].zip(true) }.should raise_error(TypeError, "wrong argument type TrueClass (must respond to :each)")
+  end
 end
diff --git a/spec/ruby/core/class/subclasses_spec.rb b/spec/ruby/core/class/subclasses_spec.rb
index ddbcfb02c0..a16b934d4f 100644
--- a/spec/ruby/core/class/subclasses_spec.rb
+++ b/spec/ruby/core/class/subclasses_spec.rb
@@ -31,6 +31,28 @@ ruby_version_is '3.1' do
       ModuleSpecs::Parent.subclasses.should == ModuleSpecs::Parent.subclasses.uniq
     end
 
+    it "works when creating subclasses concurrently" do
+      t = 16
+      n = 1000
+      go = false
+      superclass = Class.new
+
+      threads = t.times.map do
+        Thread.new do
+          Thread.pass until go
+          n.times.map do
+            Class.new(superclass)
+          end
+        end
+      end
+
+      go = true
+      classes = threads.map(&:value)
+
+      superclass.subclasses.size.should == t * n
+      superclass.subclasses.each { |c| c.should be_kind_of(Class) }
+    end
+
     def assert_subclasses(mod,subclasses)
       mod.subclasses.sort_by(&:inspect).should == subclasses.sort_by(&:inspect)
     end
diff --git a/spec/ruby/core/dir/home_spec.rb b/spec/ruby/core/dir/home_spec.rb
index cde6899df2..95bb00ad03 100644
--- a/spec/ruby/core/dir/home_spec.rb
+++ b/spec/ruby/core/dir/home_spec.rb
@@ -20,6 +20,18 @@ describe "Dir.home" do
       Dir.home.should_not.frozen?
     end
 
+    it "returns a string with the filesystem encoding" do
+      Dir.home.encoding.should == Encoding.find("filesystem")
+    end
+
+    platform_is_not :windows do
+      it "works even if HOME is unset" do
+        ENV.delete('HOME')
+        Dir.home.should.start_with?('/')
+        Dir.home.encoding.should == Encoding.find("filesystem")
+      end
+    end
+
     platform_is :windows do
       ruby_version_is "3.0" do
         it "returns the home directory with forward slashs and as UTF-8" do
@@ -29,23 +41,21 @@ describe "Dir.home" do
           home.encoding.should == Encoding::UTF_8
         end
       end
-    end
-  end
 
-  platform_is :windows do
-    it "retrieves the directory from HOME, USERPROFILE, HOMEDRIVE/HOMEPATH and the WinAPI in that order" do
-      old_dirs = [ENV.delete('HOME'), ENV.delete('USERPROFILE'), ENV.delete('HOMEDRIVE'), ENV.delete('HOMEPATH')]
+      it "retrieves the directory from HOME, USERPROFILE, HOMEDRIVE/HOMEPATH and the WinAPI in that order" do
+        old_dirs = [ENV.delete('HOME'), ENV.delete('USERPROFILE'), ENV.delete('HOMEDRIVE'), ENV.delete('HOMEPATH')]
 
-      Dir.home.should == old_dirs[1].gsub("\\", "/")
-      ENV['HOMEDRIVE'] = "C:"
-      ENV['HOMEPATH'] = "\\rubyspec\\home1"
-      Dir.home.should == "C:/rubyspec/home1"
-      ENV['USERPROFILE'] = "C:\\rubyspec\\home2"
-      Dir.home.should == "C:/rubyspec/home2"
-      ENV['HOME'] = "C:\\rubyspec\\home3"
-      Dir.home.should == "C:/rubyspec/home3"
-    ensure
-      ENV['HOME'], ENV['USERPROFILE'], ENV['HOMEDRIVE'], ENV['HOMEPATH'] = *old_dirs
+        Dir.home.should == old_dirs[1].gsub("\\", "/")
+        ENV['HOMEDRIVE'] = "C:"
+        ENV['HOMEPATH'] = "\\rubyspec\\home1"
+        Dir.home.should == "C:/rubyspec/home1"
+        ENV['USERPROFILE'] = "C:\\rubyspec\\home2"
+        Dir.home.should == "C:/rubyspec/home2"
+        ENV['HOME'] = "C:\\rubyspec\\home3"
+        Dir.home.should == "C:/rubyspec/home3"
+      ensure
+        ENV['HOME'], ENV['USERPROFILE'], ENV['HOMEDRIVE'], ENV['HOMEPATH'] = *old_dirs
+      end
     end
   end
 
@@ -65,6 +75,10 @@ describe "Dir.home" do
     it "returns a non-frozen string" do
       Dir.home(ENV['USER']).should_not.frozen?
     end
+
+    it "returns a string with the filesystem encoding" do
+      Dir.home(ENV['USER']).encoding.should == Encoding.find("filesystem")
+    end
   end
 
   it "raises an ArgumentError if the named user doesn't exist" do
diff --git a/spec/ruby/core/dir/mkdir_spec.rb b/spec/ruby/core/dir/mkdir_spec.rb
index 0ed28f5a99..076ec19dd9 100644
--- a/spec/ruby/core/dir/mkdir_spec.rb
+++ b/spec/ruby/core/dir/mkdir_spec.rb
@@ -46,7 +46,7 @@ describe "Dir.mkdir" do
     end
   end
 
-  it "calls #to_path on non-String arguments" do
+  it "calls #to_path on non-String path arguments" do
     DirSpecs.clear_dirs
     p = mock('path')
     p.should_receive(:to_path).and_return(DirSpecs.mock_dir('nonexisting'))
@@ -54,6 +54,22 @@ describe "Dir.mkdir" do
     DirSpecs.clear_dirs
   end
 
+  it "calls #to_int on non-Integer permissions argument" do
+    DirSpecs.clear_dirs
+    path = DirSpecs.mock_dir('nonexisting')
+    permissions = mock('permissions')
+    permissions.should_receive(:to_int).and_return(0666)
+    Dir.mkdir(path, permissions)
+    DirSpecs.clear_dirs
+  end
+
+  it "raises TypeError if non-Integer permissions argument does not have #to_int method" do
+    path = DirSpecs.mock_dir('nonexisting')
+    permissions = Object.new
+
+    -> { Dir.mkdir(path, permissions) }.should raise_error(TypeError, 'no implicit conversion of Object into Integer')
+  end
+
   it "raises a SystemCallError if any of the directories in the path before the last does not exist" do
     -> { Dir.mkdir "#{DirSpecs.nonexistent}/subdir" }.should raise_error(SystemCallError)
   end
diff --git a/spec/ruby/core/enumerable/zip_spec.rb b/spec/ruby/core/enumerable/zip_spec.rb
index 9ec15aa030..ab148f2a6e 100644
--- a/spec/ruby/core/enumerable/zip_spec.rb
+++ b/spec/ruby/core/enumerable/zip_spec.rb
@@ -38,4 +38,9 @@ describe "Enumerable#zip" do
     multi.zip(multi).should == [[[1, 2], [1, 2]], [[3, 4, 5], [3, 4, 5]], [[6, 7, 8, 9], [6, 7, 8, 9]]]
   end
 
+  it "raises TypeError when some argument isn't Array and doesn't respond to #to_ary and #to_enum" do
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(Object.new) }.should raise_error(TypeError, "wrong argument type Object (must respond to :each)")
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(1) }.should raise_error(TypeError, "wrong argument type Integer (must respond to :each)")
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(true) }.should raise_error(TypeError, "wrong argument type TrueClass (must respond to :each)")
+  end
 end
diff --git a/spec/ruby/core/float/comparison_spec.rb b/spec/ruby/core/float/comparison_spec.rb
index 53e7ec332a..1373b3a1fb 100644
--- a/spec/ruby/core/float/comparison_spec.rb
+++ b/spec/ruby/core/float/comparison_spec.rb
@@ -7,9 +7,25 @@ describe "Float#<=>" do
     ((bignum_value*1.1) <=> bignum_value).should == 1
   end
 
-  it "returns nil when either argument is NaN" do
-    (nan_value <=> 71.2).should be_nil
-    (1771.176 <=> nan_value).should be_nil
+  it "returns nil if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value <=> n).should == nil
+      (n <=> nan_value).should == nil
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value <=> n).should == 1
+      (n <=> infinity_value).should == -1
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value <=> n).should == -1
+      (n <=> -infinity_value).should == 1
+    }
   end
 
   it "returns nil when the given argument is not a Float" do
@@ -49,21 +65,10 @@ describe "Float#<=>" do
     }.should raise_error(TypeError, "coerce must return [x, y]")
   end
 
-  # The 4 tests below are taken from matz's revision 23730 for Ruby trunk
-  #
-  it "returns 1 when self is Infinity and other is an Integer" do
+  it "returns the correct result when one side is infinite" do
     (infinity_value <=> Float::MAX.to_i*2).should == 1
-  end
-
-  it "returns -1 when self is negative and other is Infinity" do
     (-Float::MAX.to_i*2 <=> infinity_value).should == -1
-  end
-
-  it "returns -1 when self is -Infinity and other is negative" do
     (-infinity_value <=> -Float::MAX.to_i*2).should == -1
-  end
-
-  it "returns 1 when self is negative and other is -Infinity" do
     (-Float::MAX.to_i*2 <=> -infinity_value).should == 1
   end
 
diff --git a/spec/ruby/core/float/divmod_spec.rb b/spec/ruby/core/float/divmod_spec.rb
index 523217ac1f..dad45a9b89 100644
--- a/spec/ruby/core/float/divmod_spec.rb
+++ b/spec/ruby/core/float/divmod_spec.rb
@@ -23,7 +23,7 @@ describe "Float#divmod" do
 
   # Behaviour established as correct in r23953
   it "raises a FloatDomainError if other is NaN" do
-    -> { 1.divmod(nan_value) }.should raise_error(FloatDomainError)
+    -> { 1.0.divmod(nan_value) }.should raise_error(FloatDomainError)
   end
 
   # Behaviour established as correct in r23953
diff --git a/spec/ruby/core/float/gt_spec.rb b/spec/ruby/core/float/gt_spec.rb
index 0d73f1c3df..33078e07ce 100644
--- a/spec/ruby/core/float/gt_spec.rb
+++ b/spec/ruby/core/float/gt_spec.rb
@@ -14,4 +14,25 @@ describe "Float#>" do
     -> { 5.0 > "4"       }.should raise_error(ArgumentError)
     -> { 5.0 > mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value > n).should == false
+      (n > nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value > n).should == true
+      (n > infinity_value).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value > n).should == false
+      (n > -infinity_value).should == true
+    }
+  end
 end
diff --git a/spec/ruby/core/float/gte_spec.rb b/spec/ruby/core/float/gte_spec.rb
index 98ec60b70b..44c0a81b43 100644
--- a/spec/ruby/core/float/gte_spec.rb
+++ b/spec/ruby/core/float/gte_spec.rb
@@ -14,4 +14,25 @@ describe "Float#>=" do
     -> { 5.0 >= "4"       }.should raise_error(ArgumentError)
     -> { 5.0 >= mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value >= n).should == false
+      (n >= nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value >= n).should == true
+      (n >= infinity_value).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value >= n).should == false
+      (n >= -infinity_value).should == true
+    }
+  end
 end
diff --git a/spec/ruby/core/float/lt_spec.rb b/spec/ruby/core/float/lt_spec.rb
index c01b6e0e02..94dcfc42f8 100644
--- a/spec/ruby/core/float/lt_spec.rb
+++ b/spec/ruby/core/float/lt_spec.rb
@@ -14,4 +14,25 @@ describe "Float#<" do
     -> { 5.0 < "4"       }.should raise_error(ArgumentError)
     -> { 5.0 < mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value < n).should == false
+      (n < nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value < n).should == false
+      (n < infinity_value).should == true
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value < n).should == true
+      (n < -infinity_value).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/float/lte_spec.rb b/spec/ruby/core/float/lte_spec.rb
index 66f2ddc2c7..7b5a86ee76 100644
--- a/spec/ruby/core/float/lte_spec.rb
+++ b/spec/ruby/core/float/lte_spec.rb
@@ -15,4 +15,25 @@ describe "Float#<=" do
     -> { 5.0 <= "4"       }.should raise_error(ArgumentError)
     -> { 5.0 <= mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value <= n).should == false
+      (n <= nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value <= n).should == false
+      (n <= infinity_value).should == true
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value <= n).should == true
+      (n <= -infinity_value).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/float/shared/equal.rb b/spec/ruby/core/float/shared/equal.rb
index 668aa069b5..4d524e1cf2 100644
--- a/spec/ruby/core/float/shared/equal.rb
+++ b/spec/ruby/core/float/shared/equal.rb
@@ -14,4 +14,25 @@ describe :float_equal, shared: true do
     1.0.send(@method, x).should == false
     2.0.send(@method, x).should == true
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value.send(@method, n)).should == false
+      (n.send(@method, nan_value)).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value.send(@method, n)).should == false
+      (n.send(@method, infinity_value)).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      ((-infinity_value).send(@method, n)).should == false
+      (n.send(@method, -infinity_value)).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/io/gets_spec.rb b/spec/ruby/core/io/gets_spec.rb
index 2d5e3d1ae3..1f1c3bb254 100644
--- a/spec/ruby/core/io/gets_spec.rb
+++ b/spec/ruby/core/io/gets_spec.rb
@@ -216,6 +216,10 @@ describe "IO#gets" do
     @io.gets(nil, 0).should == ""
     @io.gets("", 0).should == ""
   end
+
+  it "does not accept limit that doesn't fit in a C off_t" do
+    -> { @io.gets(2**128) }.should raise_error(RangeError)
+  end
 end
 
 describe "IO#gets" do
diff --git a/spec/ruby/core/io/lineno_spec.rb b/spec/ruby/core/io/lineno_spec.rb
index 99266ecca1..9a4ad90880 100644
--- a/spec/ruby/core/io/lineno_spec.rb
+++ b/spec/ruby/core/io/lineno_spec.rb
@@ -92,8 +92,13 @@ describe "IO#lineno=" do
     @io.lineno.should == 92233
   end
 
-  it "raises TypeError on nil argument" do
-    -> { @io.lineno = nil }.should raise_error(TypeError)
+  it "raises TypeError if cannot convert argument to Integer implicitly" do
+    -> { @io.lineno = "1" }.should raise_error(TypeError, 'no implicit conversion of String into Integer')
+    -> { @io.lineno = nil }.should raise_error(TypeError, 'no implicit conversion from nil to integer')
+  end
+
+  it "does not accept Integers that don't fit in a C int" do
+    -> { @io.lineno = 2**32 }.should raise_error(RangeError)
   end
 
   it "sets the current line number to the given value" do
diff --git a/spec/ruby/core/io/new_spec.rb b/spec/ruby/core/io/new_spec.rb
index 3597098caf..0ef30991fd 100644
--- a/spec/ruby/core/io/new_spec.rb
+++ b/spec/ruby/core/io/new_spec.rb
@@ -1,6 +1,8 @@
 require_relative '../../spec_helper'
 require_relative 'shared/new'
 
+# NOTE: should be syncronized with library/stringio/initialize_spec.rb
+
 describe "IO.new" do
   it_behaves_like :io_new, :new
 end
diff --git a/spec/ruby/core/io/readline_spec.rb b/spec/ruby/core/io/readline_spec.rb
index ca30f31e39..cf9f0dfc11 100644
--- a/spec/ruby/core/io/readline_spec.rb
+++ b/spec/ruby/core/io/readline_spec.rb
@@ -51,6 +51,10 @@ describe "IO#readline" do
     it "returns an empty string when passed 0 as a limit" do
       @io.readline(0).should == ""
     end
+
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.readline(2**128) }.should raise_error(RangeError)
+    end
   end
 
   describe "when passed separator and limit" do
diff --git a/spec/ruby/core/io/readlines_spec.rb b/spec/ruby/core/io/readlines_spec.rb
index 15af6debbe..496003002d 100644
--- a/spec/ruby/core/io/readlines_spec.rb
+++ b/spec/ruby/core/io/readlines_spec.rb
@@ -106,6 +106,10 @@ describe "IO#readlines" do
     it "raises ArgumentError when passed 0 as a limit" do
       -> { @io.readlines(0) }.should raise_error(ArgumentError)
     end
+
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.readlines(2**128) }.should raise_error(RangeError)
+    end
   end
 
   describe "when passed chomp" do
diff --git a/spec/ruby/core/io/shared/each.rb b/spec/ruby/core/io/shared/each.rb
index 1b8abce5ff..02bbe19c1a 100644
--- a/spec/ruby/core/io/shared/each.rb
+++ b/spec/ruby/core/io/shared/each.rb
@@ -77,6 +77,10 @@ describe :io_each, shared: true do
         -> { @io.send(@method, 0){} }.should raise_error(ArgumentError)
       end
     end
+
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.send(@method, 2**128){} }.should raise_error(RangeError)
+    end
   end
 
   describe "when passed a String containing one space as a separator" do
diff --git a/spec/ruby/core/io/shared/new.rb b/spec/ruby/core/io/shared/new.rb
index f2a0970a40..7677aada6e 100644
--- a/spec/ruby/core/io/shared/new.rb
+++ b/spec/ruby/core/io/shared/new.rb
@@ -1,5 +1,7 @@
 require_relative '../fixtures/classes'
 
+# NOTE: should be syncronized with library/stringio/initialize_spec.rb
+
 # This group of specs may ONLY contain specs that do successfully create
 # an IO instance from the file descriptor returned by #new_fd helper.
 describe :io_new, shared: true do
diff --git a/spec/ruby/core/io/shared/pos.rb b/spec/ruby/core/io/shared/pos.rb
index d83a6c6692..3fdd3eb2b3 100644
--- a/spec/ruby/core/io/shared/pos.rb
+++ b/spec/ruby/core/io/shared/pos.rb
@@ -60,7 +60,13 @@ describe :io_set_pos, shared: true do
     end
   end
 
-  it "does not accept Integers that don't fit in a C long" do
+  it "raises TypeError when cannot convert implicitly argument to Integer" do
+    File.open @fname do |io|
+      -> { io.send @method, Object.new }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+  end
+
+  it "does not accept Integers that don't fit in a C off_t" do
     File.open @fname do |io|
       -> { io.send @method, 2**128 }.should raise_error(RangeError)
     end
diff --git a/spec/ruby/core/io/shared/readlines.rb b/spec/ruby/core/io/shared/readlines.rb
index 479452b71c..7681e1b5c1 100644
--- a/spec/ruby/core/io/shared/readlines.rb
+++ b/spec/ruby/core/io/shared/readlines.rb
@@ -79,6 +79,10 @@ describe :io_readlines_options_19, shared: true do
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines
       end
 
+      it "does not accept Integers that don't fit in a C off_t" do
+        -> { IO.send(@method, @name, 2**128, &@object) }.should raise_error(RangeError)
+      end
+
       ruby_bug "#18767", ""..."3.3" do
         describe "when passed limit" do
           it "raises ArgumentError when passed 0 as a limit" do
diff --git a/spec/ruby/core/io/sysseek_spec.rb b/spec/ruby/core/io/sysseek_spec.rb
index e631939bce..002f2a14eb 100644
--- a/spec/ruby/core/io/sysseek_spec.rb
+++ b/spec/ruby/core/io/sysseek_spec.rb
@@ -4,7 +4,7 @@ require_relative 'fixtures/classes'
 require_relative 'shared/pos'
 
 describe "IO#sysseek" do
-  it_behaves_like :io_set_pos, :seek
+  it_behaves_like :io_set_pos, :sysseek
 end
 
 describe "IO#sysseek" do
diff --git a/spec/ruby/core/kernel/shared/load.rb b/spec/ruby/core/kernel/shared/load.rb
index cc84daeb88..5c41c19bf6 100644
--- a/spec/ruby/core/kernel/shared/load.rb
+++ b/spec/ruby/core/kernel/shared/load.rb
@@ -88,12 +88,12 @@ describe :kernel_load, shared: true do
 
   describe "when passed true for 'wrap'" do
     it "loads from an existing path" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true).should be_true
     end
 
     it "sets the enclosing scope to an anonymous module" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
       Object.const_defined?(:LoadSpecWrap).should be_false
@@ -103,14 +103,14 @@ describe :kernel_load, shared: true do
     end
 
     it "allows referencing outside namespaces" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
       ScratchPad.recorded[0].should equal(String)
     end
 
     it "sets self as a copy of the top-level main" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
       top_level = ScratchPad.recorded[2]
@@ -127,7 +127,7 @@ describe :kernel_load, shared: true do
       main_ancestors = main.singleton_class.ancestors[1..-1]
       main_ancestors.first.should == mod
 
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
       top_level = ScratchPad.recorded[2]
@@ -157,7 +157,7 @@ describe :kernel_load, shared: true do
   describe "when passed a module for 'wrap'" do
     ruby_version_is "3.1" do
       it "sets the enclosing scope to the supplied module" do
-        path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+        path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
         mod = Module.new
         @object.load(path, mod)
 
@@ -167,6 +167,25 @@ describe :kernel_load, shared: true do
         wrap_module = ScratchPad.recorded[1]
         wrap_module.should == mod
       end
+
+      it "makes constants and instance methods in the source file reachable with the supplied module" do
+        path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+        mod = Module.new
+        @object.load(path, mod)
+
+        mod::LOAD_WRAP_SPECS_TOP_LEVEL_CONSTANT.should == 1
+        obj = Object.new
+        obj.extend(mod)
+        obj.send(:load_wrap_specs_top_level_method).should == :load_wrap_specs_top_level_method
+      end
+
+      it "makes instance methods in the source file private" do
+        path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+        mod = Module.new
+        @object.load(path, mod)
+
+        mod.private_instance_methods.include?(:load_wrap_specs_top_level_method).should == true
+      end
     end
   end
 
diff --git a/spec/ruby/core/kernel/singleton_class_spec.rb b/spec/ruby/core/kernel/singleton_class_spec.rb
index a8bcd916d1..c56fa08cc1 100644
--- a/spec/ruby/core/kernel/singleton_class_spec.rb
+++ b/spec/ruby/core/kernel/singleton_class_spec.rb
@@ -1,3 +1,5 @@
+require_relative '../../spec_helper'
+
 describe "Kernel#singleton_class" do
   it "returns class extended from an object" do
     x = Object.new
diff --git a/spec/ruby/core/marshal/dump_spec.rb b/spec/ruby/core/marshal/dump_spec.rb
index 079010e554..879ea287ce 100644
--- a/spec/ruby/core/marshal/dump_spec.rb
+++ b/spec/ruby/core/marshal/dump_spec.rb
@@ -1,5 +1,6 @@
 # -*- encoding: binary -*-
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 require_relative 'fixtures/marshal_data'
 
 describe "Marshal.dump" do
@@ -106,7 +107,7 @@ describe "Marshal.dump" do
   end
 
   describe "with an object responding to #_dump" do
-    it "dumps the object returned by #marshal_dump" do
+    it "dumps the object returned by #_dump" do
       Marshal.dump(UserDefined.new).should == "\004\bu:\020UserDefined\022\004\b[\a:\nstuff;\000"
     end
 
@@ -122,6 +123,34 @@ describe "Marshal.dump" do
       m.should_not_receive(:_dump)
       Marshal.dump(m)
     end
+
+    it "indexes instance variables of a String returned by #_dump at first and then indexes the object itself" do
+      class MarshalSpec::M1::A
+        def _dump(level)
+          s = "<dump>"
+          s.instance_variable_set(:@foo, "bar")
+          s
+        end
+      end
+
+      a = MarshalSpec::M1::A.new
+
+      # 0-based index of the object a = 2, that is encoded as \x07 and printed as "\a" character.
+      # Objects are serialized in the following order: Array, a, "bar".
+      # But they are indexed in different order: Array (index=0), "bar" (index=1), a (index=2)
+      # So the second occurenc of the object a is encoded as an index 2.
+      reference = "@\a"
+      Marshal.dump([a, a]).should == "\x04\b[\aIu:\x17MarshalSpec::M1::A\v<dump>\x06:\t@foo\"\bbar#{reference}"
+    end
+
+    describe "Core library classes with #_dump returning a String with instance variables" do
+      it "indexes instance variables and then a Time object itself" do
+        t = Time.utc(2022)
+        reference = "@\a"
+
+        Marshal.dump([t, t]).should == "\x04\b[\aIu:\tTime\r \x80\x1E\xC0\x00\x00\x00\x00\x06:\tzoneI\"\bUTC\x06:\x06EF#{reference}"
+      end
+    end
   end
 
   describe "with a Class" do
@@ -185,6 +214,20 @@ describe "Marshal.dump" do
         [Marshal, -2**64, "\004\bl-\n\000\000\000\000\000\000\000\000\001\000"],
       ].should be_computed_by(:dump)
     end
+
+    it "increases the object links counter" do
+      obj = Object.new
+      object_1_link = "\x06" # representing of (0-based) index=1 (by adding 5 for small Integers)
+      object_2_link = "\x07" # representing of index=2
+
+      # objects: Array, Object, Object
+      Marshal.dump([obj, obj]).should == "\x04\b[\ao:\vObject\x00@#{object_1_link}"
+
+      # objects: Array, Bignum, Object, Object
+      Marshal.dump([2**64, obj, obj]).should == "\x04\b[\bl+\n\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+      Marshal.dump([2**48, obj, obj]).should == "\x04\b[\bl+\t\x00\x00\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+      Marshal.dump([2**32, obj, obj]).should == "\x04\b[\bl+\b\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+    end
   end
 
   describe "with a String" do
diff --git a/spec/ruby/core/marshal/fixtures/classes.rb b/spec/ruby/core/marshal/fixtures/classes.rb
new file mode 100644
index 0000000000..7c81c64927
--- /dev/null
+++ b/spec/ruby/core/marshal/fixtures/classes.rb
@@ -0,0 +1,4 @@
+module MarshalSpec
+  # empty modules
+  module M1 end
+end
diff --git a/spec/ruby/core/matchdata/values_at_spec.rb b/spec/ruby/core/matchdata/values_at_spec.rb
index 8f7fdf557c..4fd0bfc42a 100644
--- a/spec/ruby/core/matchdata/values_at_spec.rb
+++ b/spec/ruby/core/matchdata/values_at_spec.rb
@@ -1,21 +1,76 @@
 require_relative '../../spec_helper'
 
-describe "MatchData#values_at" do
-  it "returns an array of the matching value" do
-    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+describe "Struct#values_at" do
+  # Should be synchronized with core/array/values_at_spec.rb and core/struct/values_at_spec.rb
+  #
+  # /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").to_a # => ["HX1138", "H", "X", "113", "8"]
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+    end
+
+    it "returns nil value for any integer that is out of range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(5).should == [nil]
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6).should == [nil]
+    end
   end
 
-  describe "when passed a Range" do
-    it "returns an array of the matching value" do
-      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..4, 0..1).should == ["X", "113", "8", "HX1138", "H"]
+  context "when passed an integer Range" do
+    it "returns an array containing each value given by the elements of the range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "fills with nil values for range elements larger than the captured values number" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..5).should == ["HX1138", "H", "X", "113", "8", nil]
+    end
+
+    it "raises RangeError if any element of the range is negative and out of range" do
+      -> { /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6..3) }.should raise_error(RangeError, "-6..3 out of range")
+    end
+
+    it "supports endless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..).should == ["HX1138", "H", "X", "113", "8"]
+    end
+
+    it "supports beginningless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "returns an empty Array when Range is empty" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..0).should == []
+    end
+  end
+
+  context "when passed names" do
+    it 'slices captures with the given names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+    end
+
+    it 'slices captures with the given String names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at('c', 'a').should == ['2', '0']
     end
   end
 
-  it 'slices captures with the given names' do
-    /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+  it "supports multiple integer Ranges" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 2..3).should == ["H", "X", "X", "113"]
   end
 
-  it 'takes names and indices' do
+  it "supports mixing integer Ranges and Integers" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 4).should == ["H", "X", "8"]
+  end
+
+  it 'supports mixing of names and indices' do
     /\A(?<a>.)(?<b>.)\z/.match('01').values_at(0, 1, 2, :a, :b).should == ['01', '0', '1', '0', '1']
   end
+
+  it "returns a new empty Array if no arguments given" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at().should == []
+  end
+
+  it "fails when passed arguments of unsupported types" do
+    -> {
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+  end
 end
diff --git a/spec/ruby/core/module/fixtures/classes.rb b/spec/ruby/core/module/fixtures/classes.rb
index 2b47ff112e..bc6b940a6c 100644
--- a/spec/ruby/core/module/fixtures/classes.rb
+++ b/spec/ruby/core/module/fixtures/classes.rb
@@ -388,6 +388,7 @@ module ModuleSpecs
   # empty modules
   module M1; end
   module M2; end
+  module M3; end
 
   module Autoload
     def self.use_ex1
diff --git a/spec/ruby/core/module/include_spec.rb b/spec/ruby/core/module/include_spec.rb
index c47e052d22..c073bc31ca 100644
--- a/spec/ruby/core/module/include_spec.rb
+++ b/spec/ruby/core/module/include_spec.rb
@@ -104,9 +104,9 @@ describe "Module#include" do
       class A; include M; end
       class B < A; include M; end
 
-      all = [A,B,M]
+      all = [A, B, M]
 
-      (B.ancestors & all).should == [B, A, M]
+      (B.ancestors.filter { |a| all.include?(a) }).should == [B, A, M]
     end
   end
 
diff --git a/spec/ruby/core/module/prepend_spec.rb b/spec/ruby/core/module/prepend_spec.rb
index d636e023ed..976b09b105 100644
--- a/spec/ruby/core/module/prepend_spec.rb
+++ b/spec/ruby/core/module/prepend_spec.rb
@@ -611,6 +611,18 @@ describe "Module#prepend" do
     ScratchPad.recorded.should == [[:prepend_features, c], [:prepended, c]]
   end
 
+  it "prepends a module if it is included in a super class" do
+    module ModuleSpecs::M3
+      module M; end
+      class A; include M; end
+      class B < A; prepend M; end
+
+      all = [A, B, M]
+
+      (B.ancestors.filter { |a| all.include?(a) }).should == [M, B, A, M]
+    end
+  end
+
   it "detects cyclic prepends" do
     -> {
       module ModuleSpecs::P
diff --git a/spec/ruby/core/objectspace/define_finalizer_spec.rb b/spec/ruby/core/objectspace/define_finalizer_spec.rb
index 281785b0a4..d9db027e0b 100644
--- a/spec/ruby/core/objectspace/define_finalizer_spec.rb
+++ b/spec/ruby/core/objectspace/define_finalizer_spec.rb
@@ -169,4 +169,26 @@ describe "ObjectSpace.define_finalizer" do
 
     ruby_exe(code).lines.sort.should == ["finalized1\n", "finalized2\n"]
   end
+
+  ruby_version_is "3.1" do
+    describe "when $VERBOSE is not nil" do
+      it "warns if an exception is raised in finalizer" do
+        code = <<-RUBY
+          ObjectSpace.define_finalizer(Object.new) { raise "finalizing" }
+        RUBY
+
+        ruby_exe(code, args: "2>&1").should include("warning: Exception in finalizer", "finalizing")
+      end
+    end
+
+    describe "when $VERBOSE is nil" do
+      it "does not warn even if an exception is raised in finalizer" do
+        code = <<-RUBY
+          ObjectSpace.define_finalizer(Object.new) { raise "finalizing" }
+        RUBY
+
+        ruby_exe(code, args: "2>&1", options: "-W0").should == ""
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/process/constants_spec.rb b/spec/ruby/core/process/constants_spec.rb
index b61f5ab64e..4130bb58a5 100644
--- a/spec/ruby/core/process/constants_spec.rb
+++ b/spec/ruby/core/process/constants_spec.rb
@@ -1,3 +1,4 @@
+require_relative '../../spec_helper'
 
 describe "Process::Constants" do
   platform_is :darwin, :netbsd, :freebsd do
diff --git a/spec/ruby/core/process/detach_spec.rb b/spec/ruby/core/process/detach_spec.rb
index 1c27ed9c2c..91661afcea 100644
--- a/spec/ruby/core/process/detach_spec.rb
+++ b/spec/ruby/core/process/detach_spec.rb
@@ -42,5 +42,34 @@ describe "Process.detach" do
 
       thr.pid.should == pid
     end
+
+    it "tolerates not existing child process pid" do
+      # ensure there is no child process with this hardcoded pid
+      # `kill 0 pid` for existing process returns "1" and raises Errno::ESRCH if process doesn't exist
+      -> {  Process.kill(0, 100500) }.should raise_error(Errno::ESRCH)
+
+      thr = Process.detach(100500)
+      thr.join
+
+      thr.should be_kind_of(Thread)
+    end
+
+    it "calls #to_int to implicitly convert non-Integer pid to Integer" do
+      pid = MockObject.new('mock-enumerable')
+      pid.should_receive(:to_int).and_return(100500)
+
+      Process.detach(pid).join
+    end
+
+    it "raises TypeError when pid argument does not have #to_int method" do
+      -> { Process.detach(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "raises TypeError when #to_int returns non-Integer value" do
+      pid = MockObject.new('mock-enumerable')
+      pid.should_receive(:to_int).and_return(:symbol)
+
+      -> { Process.detach(pid) }.should raise_error(TypeError, "can't convert MockObject to Integer (MockObject#to_int gives Symbol)")
+    end
   end
 end
diff --git a/spec/ruby/core/process/spawn_spec.rb b/spec/ruby/core/process/spawn_spec.rb
index ad4800d4f8..7a280ccdf4 100644
--- a/spec/ruby/core/process/spawn_spec.rb
+++ b/spec/ruby/core/process/spawn_spec.rb
@@ -477,6 +477,16 @@ describe "Process.spawn" do
 
   # redirection
 
+  it 'redirects to the wrapped IO using wrapped_io.to_io if out: wrapped_io' do
+    File.open(@name, 'w') do |file|
+      -> do
+        wrapped_io = mock('wrapped IO')
+        wrapped_io.should_receive(:to_io).and_return(file)
+        Process.wait Process.spawn('echo "Hello World"', out: wrapped_io)
+      end.should output_to_fd("Hello World\n", file)
+    end
+  end
+
   it "redirects STDOUT to the given file descriptor if out: Integer" do
     File.open(@name, 'w') do |file|
       -> do
diff --git a/spec/ruby/core/process/times_spec.rb b/spec/ruby/core/process/times_spec.rb
index d114061eb6..6142cd257c 100644
--- a/spec/ruby/core/process/times_spec.rb
+++ b/spec/ruby/core/process/times_spec.rb
@@ -7,7 +7,7 @@ describe "Process.times" do
 
   # TODO: Intel C Compiler does not work this example
   # http://rubyci.s3.amazonaws.com/icc-x64/ruby-master/log/20221013T030005Z.fail.html.gz
-  unless RbConfig::CONFIG['CC'].include?("icx")
+  unless RbConfig::CONFIG['CC']&.include?("icx")
     it "returns current cpu times" do
       t = Process.times
       user = t.utime
diff --git a/spec/ruby/core/queue/initialize_spec.rb b/spec/ruby/core/queue/initialize_spec.rb
index 83c7e595fe..c45abcd29d 100644
--- a/spec/ruby/core/queue/initialize_spec.rb
+++ b/spec/ruby/core/queue/initialize_spec.rb
@@ -7,6 +7,10 @@ describe "Queue#initialize" do
     q.should.empty?
   end
 
+  it "is a private method" do
+    Queue.private_instance_methods.include?(:initialize).should == true
+  end
+
   ruby_version_is '3.1' do
     it "adds all elements of the passed Enumerable to self" do
       q = Queue.new([1, 2, 3])
@@ -30,9 +34,16 @@ describe "Queue#initialize" do
       q.should.empty?
     end
 
-    it "raises if the provided Enumerable does not respond to #to_a" do
+    it "raises TypeError if the provided Enumerable does not respond to #to_a" do
       enumerable = MockObject.new('mock-enumerable')
       -> { Queue.new(enumerable) }.should raise_error(TypeError, "can't convert MockObject into Array")
     end
+
+    it "raises TypeError if #to_a does not return Array" do
+      enumerable = MockObject.new('mock-enumerable')
+      enumerable.should_receive(:to_a).and_return("string")
+
+      -> { Queue.new(enumerable) }.should raise_error(TypeError, "can't convert MockObject to Array (MockObject#to_a gives String)")
+    end
   end
 end
diff --git a/spec/ruby/core/refinement/import_methods_spec.rb b/spec/ruby/core/refinement/import_methods_spec.rb
new file mode 100644
index 0000000000..1c526f5822
--- /dev/null
+++ b/spec/ruby/core/refinement/import_methods_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#import_methods" do
+  ruby_version_is "3.1" do
+    context "when methods are defined in Ruby code" do
+      it "imports methods" do
+        str_utils = Module.new do
+          def indent(level)
+            " " * level + self
+          end
+        end
+
+        Module.new do
+          refine String do
+            import_methods str_utils
+            "foo".indent(3).should == "   foo"
+          end
+        end
+      end
+    end
+
+    context "when methods are not defined in Ruby code" do
+      it "raises ArgumentError" do
+        Module.new do
+          refine String do
+            -> {
+              import_methods Kernel
+            }.should raise_error(ArgumentError)
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/include_spec.rb b/spec/ruby/core/refinement/include_spec.rb
new file mode 100644
index 0000000000..25a53f0ec7
--- /dev/null
+++ b/spec/ruby/core/refinement/include_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#include" do
+  ruby_version_is "3.1"..."3.2" do
+    it "warns about deprecation" do
+      Module.new do
+        refine String do
+          -> {
+            include Module.new
+          }.should complain(/warning: Refinement#include is deprecated and will be removed in Ruby 3.2/)
+        end
+      end
+    end
+  end
+
+  ruby_version_is "3.2" do
+    it "raises a TypeError" do
+      Module.new do
+        refine String do
+          -> {
+            include Module.new
+          }.should raise_error(TypeError, "Refinement#include has been removed")
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/prepend_spec.rb b/spec/ruby/core/refinement/prepend_spec.rb
new file mode 100644
index 0000000000..27b70d392a
--- /dev/null
+++ b/spec/ruby/core/refinement/prepend_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#prepend" do
+  ruby_version_is "3.1"..."3.2" do
+    it "warns about deprecation" do
+      Module.new do
+        refine String do
+          -> {
+            prepend Module.new
+          }.should complain(/warning: Refinement#prepend is deprecated and will be removed in Ruby 3.2/)
+        end
+      end
+    end
+  end
+
+  ruby_version_is "3.2" do
+    it "raises a TypeError" do
+      Module.new do
+        refine String do
+          -> {
+            prepend Module.new
+          }.should raise_error(TypeError, "Refinement#prepend has been removed")
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/regexp/initialize_spec.rb b/spec/ruby/core/regexp/initialize_spec.rb
index 772a233e82..a1583384af 100644
--- a/spec/ruby/core/regexp/initialize_spec.rb
+++ b/spec/ruby/core/regexp/initialize_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Regexp#initialize" do
   it "is a private method" do
-    Regexp.should have_private_method(:initialize)
+    Regexp.should have_private_instance_method(:initialize)
   end
 
   ruby_version_is ""..."3.0" do
diff --git a/spec/ruby/core/signal/trap_spec.rb b/spec/ruby/core/signal/trap_spec.rb
index 2a94a81634..10e122e072 100644
--- a/spec/ruby/core/signal/trap_spec.rb
+++ b/spec/ruby/core/signal/trap_spec.rb
@@ -221,6 +221,18 @@ describe "Signal.trap" do
       Signal.trap(:HUP, @saved_trap).should equal(@proc)
     end
 
+    it "raises ArgumentError when passed unknown signal" do
+      -> { Signal.trap(300) { } }.should raise_error(ArgumentError, "invalid signal number (300)")
+      -> { Signal.trap("USR10") { } }.should raise_error(ArgumentError, "unsupported signal `SIGUSR10'")
+      -> { Signal.trap("SIGUSR10") { } }.should raise_error(ArgumentError, "unsupported signal `SIGUSR10'")
+    end
+
+    it "raises ArgumentError when passed signal is not Integer, String or Symbol" do
+      -> { Signal.trap(nil) { } }.should raise_error(ArgumentError, "bad signal type NilClass")
+      -> { Signal.trap(100.0) { } }.should raise_error(ArgumentError, "bad signal type Float")
+      -> { Signal.trap(Rational(100)) { } }.should raise_error(ArgumentError, "bad signal type Rational")
+    end
+
     # See man 2 signal
     %w[KILL STOP].each do |signal|
       it "raises ArgumentError or Errno::EINVAL for SIG#{signal}" do
diff --git a/spec/ruby/core/string/byteslice_spec.rb b/spec/ruby/core/string/byteslice_spec.rb
index a49da040eb..312229523d 100644
--- a/spec/ruby/core/string/byteslice_spec.rb
+++ b/spec/ruby/core/string/byteslice_spec.rb
@@ -24,4 +24,10 @@ describe "String#byteslice on on non ASCII strings" do
     "\u3042".byteslice(1..2).should == "\x81\x82".force_encoding("UTF-8")
     "\u3042".byteslice(-1).should == "\x82".force_encoding("UTF-8")
   end
+
+  it "returns a String in the same encoding as self" do
+    "ruby".encode("UTF-8").slice(0).encoding.should == Encoding::UTF_8
+    "ruby".encode("US-ASCII").slice(0).encoding.should == Encoding::US_ASCII
+    "ruby".encode("Windows-1251").slice(0).encoding.should == Encoding::Windows_1251
+  end
 end
diff --git a/spec/ruby/core/string/capitalize_spec.rb b/spec/ruby/core/string/capitalize_spec.rb
index 751f4160a6..3f85cf5ae4 100644
--- a/spec/ruby/core/string/capitalize_spec.rb
+++ b/spec/ruby/core/string/capitalize_spec.rb
@@ -91,6 +91,10 @@ describe "String#capitalize" do
       StringSpecs::MyString.new("Hello").capitalize.should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    "h".encode("US-ASCII").capitalize.encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#capitalize!" do
diff --git a/spec/ruby/core/string/chars_spec.rb b/spec/ruby/core/string/chars_spec.rb
index e4f26bc0cc..715e65dc90 100644
--- a/spec/ruby/core/string/chars_spec.rb
+++ b/spec/ruby/core/string/chars_spec.rb
@@ -1,5 +1,4 @@
 require_relative 'shared/chars'
-require_relative 'shared/each_char_without_block'
 
 describe "String#chars" do
   it_behaves_like :string_chars, :chars
@@ -7,4 +6,10 @@ describe "String#chars" do
   it "returns an array when no block given" do
     "hello".chars.should == ['h', 'e', 'l', 'l', 'o']
   end
+
+  it "returns Strings in the same encoding as self" do
+    "hello".encode("US-ASCII").chars.each do |c|
+      c.encoding.should == Encoding::US_ASCII
+    end
+  end
 end
diff --git a/spec/ruby/core/string/chomp_spec.rb b/spec/ruby/core/string/chomp_spec.rb
index c03bfc7951..d0508d938f 100644
--- a/spec/ruby/core/string/chomp_spec.rb
+++ b/spec/ruby/core/string/chomp_spec.rb
@@ -40,6 +40,10 @@ describe "String#chomp" do
       "".chomp.should == ""
     end
 
+    it "returns a String in the same encoding as self" do
+      "abc\n\n".encode("US-ASCII").chomp.encoding.should == Encoding::US_ASCII
+    end
+
     ruby_version_is ''...'3.0' do
       it "returns subclass instances when called on a subclass" do
         str = StringSpecs::MyString.new("hello\n").chomp
diff --git a/spec/ruby/core/string/chop_spec.rb b/spec/ruby/core/string/chop_spec.rb
index 266d973f67..f598d34bc8 100644
--- a/spec/ruby/core/string/chop_spec.rb
+++ b/spec/ruby/core/string/chop_spec.rb
@@ -60,6 +60,10 @@ describe "String#chop" do
       StringSpecs::MyString.new("hello\n").chop.should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    "abc\n\n".encode("US-ASCII").chop.encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#chop!" do
diff --git a/spec/ruby/core/string/clone_spec.rb b/spec/ruby/core/string/clone_spec.rb
index f8d40423f0..a2ba2f9877 100644
--- a/spec/ruby/core/string/clone_spec.rb
+++ b/spec/ruby/core/string/clone_spec.rb
@@ -54,4 +54,8 @@ describe "String#clone" do
     orig.should == "xtring"
     clone.should == "string"
   end
+
+  it "returns a String in the same encoding as self" do
+    "a".encode("US-ASCII").clone.encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/string/delete_prefix_spec.rb b/spec/ruby/core/string/delete_prefix_spec.rb
index 17ce18bcca..238de85f05 100644
--- a/spec/ruby/core/string/delete_prefix_spec.rb
+++ b/spec/ruby/core/string/delete_prefix_spec.rb
@@ -51,6 +51,10 @@ describe "String#delete_prefix" do
       s.delete_prefix('hell').should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    'hello'.encode("US-ASCII").delete_prefix('hell').encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#delete_prefix!" do
diff --git a/spec/ruby/core/string/delete_spec.rb b/spec/ruby/core/string/delete_spec.rb
index b91e88b76f..87831a9d19 100644
--- a/spec/ruby/core/string/delete_spec.rb
+++ b/spec/ruby/core/string/delete_spec.rb
@@ -95,6 +95,10 @@ describe "String#delete" do
       StringSpecs::MyString.new("oh no!!!").delete("!").should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").delete("lo").encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#delete!" do
diff --git a/spec/ruby/core/string/delete_suffix_spec.rb b/spec/ruby/core/string/delete_suffix_spec.rb
index 0705c73246..6883d6938c 100644
--- a/spec/ruby/core/string/delete_suffix_spec.rb
+++ b/spec/ruby/core/string/delete_suffix_spec.rb
@@ -51,6 +51,10 @@ describe "String#delete_suffix" do
       s.delete_suffix('ello').should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").delete_suffix("ello").encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#delete_suffix!" do
diff --git a/spec/ruby/core/string/downcase_spec.rb b/spec/ruby/core/string/downcase_spec.rb
index f0a15f1e25..153b4ce191 100644
--- a/spec/ruby/core/string/downcase_spec.rb
+++ b/spec/ruby/core/string/downcase_spec.rb
@@ -8,6 +8,10 @@ describe "String#downcase" do
     "hello".downcase.should == "hello"
   end
 
+  it "returns a String in the same encoding as self" do
+    "hELLO".encode("US-ASCII").downcase.encoding.should == Encoding::US_ASCII
+  end
+
   describe "full Unicode case mapping" do
     it "works for all of Unicode with no option" do
       "ÄÖÜ".downcase.should == "äöü"
diff --git a/spec/ruby/core/string/dump_spec.rb b/spec/ruby/core/string/dump_spec.rb
index 79a8b55e6d..81de0cfae4 100644
--- a/spec/ruby/core/string/dump_spec.rb
+++ b/spec/ruby/core/string/dump_spec.rb
@@ -350,7 +350,7 @@ describe "String#dump" do
     ].should be_computed_by(:dump)
   end
 
-  it "returns a string with multi-byte UTF-8 characters replaced by \\u{} notation with upper-case hex digits" do
+  it "returns a string with multi-byte UTF-8 characters less than or equal 0xFFFF replaced by \\uXXXX notation with upper-case hex digits" do
     [ [0200.chr('utf-8'), '"\u0080"'],
       [0201.chr('utf-8'), '"\u0081"'],
       [0202.chr('utf-8'), '"\u0082"'],
@@ -382,15 +382,21 @@ describe "String#dump" do
       [0235.chr('utf-8'), '"\u009D"'],
       [0236.chr('utf-8'), '"\u009E"'],
       [0237.chr('utf-8'), '"\u009F"'],
+      [0177777.chr('utf-8'), '"\uFFFF"'],
     ].should be_computed_by(:dump)
   end
 
+  it "returns a string with multi-byte UTF-8 characters greater than 0xFFFF replaced by \\u{XXXXXX} notation with upper-case hex digits" do
+    0x10000.chr('utf-8').dump.should == '"\u{10000}"'
+    0x10FFFF.chr('utf-8').dump.should == '"\u{10FFFF}"'
+  end
+
   it "includes .force_encoding(name) if the encoding isn't ASCII compatible" do
     "\u{876}".encode('utf-16be').dump.should.end_with?(".force_encoding(\"UTF-16BE\")")
     "\u{876}".encode('utf-16le').dump.should.end_with?(".force_encoding(\"UTF-16LE\")")
   end
 
-  it "keeps origin encoding" do
+  it "returns a String in the same encoding as self" do
     "foo".encode("ISO-8859-1").dump.encoding.should == Encoding::ISO_8859_1
     "foo".encode('windows-1251').dump.encoding.should == Encoding::Windows_1251
     1.chr.dump.encoding.should == Encoding::US_ASCII
diff --git a/spec/ruby/core/string/dup_spec.rb b/spec/ruby/core/string/dup_spec.rb
index eec3cf0a70..73f71b8ffc 100644
--- a/spec/ruby/core/string/dup_spec.rb
+++ b/spec/ruby/core/string/dup_spec.rb
@@ -58,4 +58,8 @@ describe "String#dup" do
     orig.should == "c"
     copy.should == "b"
   end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").dup.encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/string/lines_spec.rb b/spec/ruby/core/string/lines_spec.rb
index ad4b119074..40ab5f71d8 100644
--- a/spec/ruby/core/string/lines_spec.rb
+++ b/spec/ruby/core/string/lines_spec.rb
@@ -1,7 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/each_line'
-require_relative 'shared/each_line_without_block'
 
 describe "String#lines" do
   it_behaves_like :string_each_line, :lines
diff --git a/spec/ruby/core/string/reverse_spec.rb b/spec/ruby/core/string/reverse_spec.rb
index 4206b8af90..73526256ef 100644
--- a/spec/ruby/core/string/reverse_spec.rb
+++ b/spec/ruby/core/string/reverse_spec.rb
@@ -37,6 +37,10 @@ describe "String#reverse" do
 
     str.reverse.should == "體黑正\xDE\xDF軟微"
   end
+
+  it "returns a String in the same encoding as self" do
+    "stressed".encode("US-ASCII").reverse.encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#reverse!" do
diff --git a/spec/ruby/core/string/scan_spec.rb b/spec/ruby/core/string/scan_spec.rb
index ab73f5747b..a2d1815132 100644
--- a/spec/ruby/core/string/scan_spec.rb
+++ b/spec/ruby/core/string/scan_spec.rb
@@ -69,6 +69,12 @@ describe "String#scan" do
   it "does not raise any errors when passed a multi-byte string" do
     "あああaaaあああ".scan("あああ").should == ["あああ", "あああ"]
   end
+
+  it "returns Strings in the same encoding as self" do
+    "cruel world".encode("US-ASCII").scan(/\w+/).each do |s|
+      s.encoding.should == Encoding::US_ASCII
+    end
+  end
 end
 
 describe "String#scan with pattern and block" do
diff --git a/spec/ruby/core/string/scrub_spec.rb b/spec/ruby/core/string/scrub_spec.rb
index 66755bcc7b..a51fbd020a 100644
--- a/spec/ruby/core/string/scrub_spec.rb
+++ b/spec/ruby/core/string/scrub_spec.rb
@@ -31,6 +31,11 @@ describe "String#scrub with a default replacement" do
     input.scrub.should == "abc?????"
   end
 
+  it "returns a String in the same encoding as self" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    "abc\u3042#{x81}".scrub.encoding.should == Encoding::UTF_8
+  end
+
   ruby_version_is '3.0' do
     it "returns String instances when called on a subclass" do
       StringSpecs::MyString.new("foo").scrub.should be_an_instance_of(String)
@@ -80,6 +85,11 @@ describe "String#scrub with a custom replacement" do
     block.should raise_error(ArgumentError)
   end
 
+  it "returns a String in the same encoding as self" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    "abc\u3042#{x81}".scrub("*").encoding.should == Encoding::UTF_8
+  end
+
   it "raises TypeError when a non String replacement is given" do
     x81 = [0x81].pack('C').force_encoding('utf-8')
     block = -> { "foo#{x81}".scrub(1) }
diff --git a/spec/ruby/core/string/shared/each_line.rb b/spec/ruby/core/string/shared/each_line.rb
index bfedf8f35a..df78bd2186 100644
--- a/spec/ruby/core/string/shared/each_line.rb
+++ b/spec/ruby/core/string/shared/each_line.rb
@@ -122,6 +122,12 @@ describe :string_each_line, shared: true do
     out.should == ["hello\n", "world."]
   end
 
+  it "returns Strings in the same encoding as self" do
+    "one\ntwo\r\nthree".encode("US-ASCII").send(@method) do |s|
+      s.encoding.should == Encoding::US_ASCII
+    end
+  end
+
   it "raises a TypeError when the separator can't be converted to a string" do
     -> { "hello world".send(@method, false) {}     }.should raise_error(TypeError)
     -> { "hello world".send(@method, mock('x')) {} }.should raise_error(TypeError)
diff --git a/spec/ruby/core/string/shared/partition.rb b/spec/ruby/core/string/shared/partition.rb
index 7dc3d9cc0b..41b3c7e0c9 100644
--- a/spec/ruby/core/string/shared/partition.rb
+++ b/spec/ruby/core/string/shared/partition.rb
@@ -33,4 +33,19 @@ describe :string_partition, shared: true do
       end
     end
   end
+
+  it "returns before- and after- parts in the same encoding as self" do
+    strings = "hello".encode("US-ASCII").send(@method, "ello")
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[2].encoding.should == Encoding::US_ASCII
+
+    strings = "hello".encode("US-ASCII").send(@method, /ello/)
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[2].encoding.should == Encoding::US_ASCII
+  end
+
+  it "returns the matching part in the separator's encoding" do
+    strings = "hello".encode("US-ASCII").send(@method, "ello")
+    strings[1].encoding.should == Encoding::UTF_8
+  end
 end
diff --git a/spec/ruby/core/string/shared/slice.rb b/spec/ruby/core/string/shared/slice.rb
index 713234fffd..a7c1d05b56 100644
--- a/spec/ruby/core/string/shared/slice.rb
+++ b/spec/ruby/core/string/shared/slice.rb
@@ -80,7 +80,7 @@ describe :string_slice_index_length, shared: true do
     "hello there".send(@method, -3,2).should == "er"
   end
 
-  it "returns a string with the same encoding" do
+  it "returns a string with the same encoding as self" do
     s = "hello there"
     s.send(@method, 1, 9).encoding.should == s.encoding
 
@@ -206,6 +206,10 @@ describe :string_slice_range, shared: true do
     "x".send(@method, 1..-1).should == ""
   end
 
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, 1..1).encoding.should == Encoding::US_ASCII
+  end
+
   it "returns nil if the beginning of the range falls outside of self" do
     "hello there".send(@method, 12..-1).should == nil
     "hello there".send(@method, 20..25).should == nil
@@ -328,7 +332,8 @@ describe :string_slice_regexp, shared: true do
     "hello there".send(@method, /xyz/).should == nil
   end
 
-  not_supported_on :opal do
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, /[aeiou](.)\1/).encoding.should == Encoding::US_ASCII
   end
 
   ruby_version_is ''...'3.0' do
@@ -391,6 +396,10 @@ describe :string_slice_regexp_index, shared: true do
     $~[1].should == nil
   end
 
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, /[aeiou](.)\1/, 0).encoding.should == Encoding::US_ASCII
+  end
+
   it "calls to_int on the given index" do
     obj = mock('2')
     obj.should_receive(:to_int).and_return(2)
diff --git a/spec/ruby/core/string/shared/strip.rb b/spec/ruby/core/string/shared/strip.rb
index 9c232b4694..0c0aae20f3 100644
--- a/spec/ruby/core/string/shared/strip.rb
+++ b/spec/ruby/core/string/shared/strip.rb
@@ -2,6 +2,10 @@ require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
 describe :string_strip, shared: true do
+  it "returns a String in the same encoding as self" do
+    " hello ".encode("US-ASCII").send(@method).encoding.should == Encoding::US_ASCII
+  end
+
   ruby_version_is '3.0' do
     it "returns String instances when called on a subclass" do
       StringSpecs::MyString.new(" hello ").send(@method).should be_an_instance_of(String)
diff --git a/spec/ruby/core/string/shared/succ.rb b/spec/ruby/core/string/shared/succ.rb
index 66edf6dc82..3605fa99a2 100644
--- a/spec/ruby/core/string/shared/succ.rb
+++ b/spec/ruby/core/string/shared/succ.rb
@@ -74,6 +74,10 @@ describe :string_succ, shared: true do
       StringSpecs::MyString.new("z").send(@method).should be_an_instance_of(String)
     end
   end
+
+  it "returns a String in the same encoding as self" do
+    "z".encode("US-ASCII").send(@method).encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe :string_succ_bang, shared: true do
diff --git a/spec/ruby/core/string/split_spec.rb b/spec/ruby/core/string/split_spec.rb
index 0417486692..519c5d845d 100644
--- a/spec/ruby/core/string/split_spec.rb
+++ b/spec/ruby/core/string/split_spec.rb
@@ -246,6 +246,13 @@ describe "String#split with String" do
   it "doesn't split on non-ascii whitespace" do
     "a\u{2008}b".split(" ").should == ["a\u{2008}b"]
   end
+
+  it "returns Strings in the same encoding as self" do
+    strings = "hello world".encode("US-ASCII").split(" ")
+
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[1].encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#split with Regexp" do
@@ -443,13 +450,12 @@ describe "String#split with Regexp" do
     end
   end
 
-  it "retains the encoding of the source string" do
+  it "returns Strings in the same encoding as self" do
     ary = "а б в".split
     encodings = ary.map { |s| s.encoding }
     encodings.should == [Encoding::UTF_8, Encoding::UTF_8, Encoding::UTF_8]
   end
 
-
   it "splits a string on each character for a multibyte encoding and empty split" do
     "That's why efficiency could not be helped".split("").size.should == 39
   end
@@ -598,4 +604,11 @@ describe "String#split with Regexp" do
     -> { "hello".split(false) }.should raise_error(TypeError)
     -> { "hello".split(Object.new) }.should raise_error(TypeError)
   end
+
+  it "returns Strings in the same encoding as self" do
+    strings = "hello world".encode("US-ASCII").split(/ /)
+
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[1].encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/string/squeeze_spec.rb b/spec/ruby/core/string/squeeze_spec.rb
index 5dc12a4247..2f3fa65745 100644
--- a/spec/ruby/core/string/squeeze_spec.rb
+++ b/spec/ruby/core/string/squeeze_spec.rb
@@ -64,6 +64,11 @@ describe "String#squeeze" do
     "hello room".squeeze(other_string, other_string2).should == "hello rom"
   end
 
+  it "returns a String in the same encoding as self" do
+    "yellow moon".encode("US-ASCII").squeeze.encoding.should == Encoding::US_ASCII
+    "yellow moon".encode("US-ASCII").squeeze("a").encoding.should == Encoding::US_ASCII
+  end
+
   it "raises a TypeError when one set arg can't be converted to a string" do
     -> { "hello world".squeeze([])        }.should raise_error(TypeError)
     -> { "hello world".squeeze(Object.new)}.should raise_error(TypeError)
diff --git a/spec/ruby/core/string/swapcase_spec.rb b/spec/ruby/core/string/swapcase_spec.rb
index 6307a1eaaf..d369ab3e4e 100644
--- a/spec/ruby/core/string/swapcase_spec.rb
+++ b/spec/ruby/core/string/swapcase_spec.rb
@@ -9,6 +9,10 @@ describe "String#swapcase" do
    "+++---111222???".swapcase.should == "+++---111222???"
   end
 
+  it "returns a String in the same encoding as self" do
+    "Hello".encode("US-ASCII").swapcase.encoding.should == Encoding::US_ASCII
+  end
+
   describe "full Unicode case mapping" do
     it "works for all of Unicode with no option" do
       "äÖü".swapcase.should == "ÄöÜ"
diff --git a/spec/ruby/core/string/undump_spec.rb b/spec/ruby/core/string/undump_spec.rb
index 08058d9bd1..6ff220161c 100644
--- a/spec/ruby/core/string/undump_spec.rb
+++ b/spec/ruby/core/string/undump_spec.rb
@@ -389,7 +389,7 @@ describe "String#undump" do
     '"\\bv".force_encoding("UTF-16BE")'.undump.should == "\u0876".encode('utf-16be')
   end
 
-  it "keeps origin encoding" do
+  it "returns a String in the same encoding as self" do
     '"foo"'.encode("ISO-8859-1").undump.encoding.should == Encoding::ISO_8859_1
     '"foo"'.encode('windows-1251').undump.encoding.should == Encoding::Windows_1251
   end
diff --git a/spec/ruby/core/string/unpack/b_spec.rb b/spec/ruby/core/string/unpack/b_spec.rb
index fcabc99731..2cf5ebad34 100644
--- a/spec/ruby/core/string/unpack/b_spec.rb
+++ b/spec/ruby/core/string/unpack/b_spec.rb
@@ -86,8 +86,18 @@ describe "String#unpack with format 'B'" do
     ].should be_computed_by(:unpack, "BBB")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x80\x00".unpack("B\x00B").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x80\x00".unpack("B\x00B").should == ["1", "0"]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x80\x00".unpack("B\x00B")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -182,8 +192,18 @@ describe "String#unpack with format 'b'" do
     ].should be_computed_by(:unpack, "bbb")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x00".unpack("b\x00b").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x01\x00".unpack("b\x00b").should == ["1", "0"]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x00".unpack("b\x00b")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/c_spec.rb b/spec/ruby/core/string/unpack/c_spec.rb
index ed8caa4895..dbcbacc74d 100644
--- a/spec/ruby/core/string/unpack/c_spec.rb
+++ b/spec/ruby/core/string/unpack/c_spec.rb
@@ -35,8 +35,18 @@ describe :string_unpack_8bit, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abc".unpack(unpack_format("\000", 2)).should == [97, 98]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "abc".unpack(unpack_format("\000", 2)).should == [97, 98]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/h_spec.rb b/spec/ruby/core/string/unpack/h_spec.rb
index f2f5dcf396..ee08d20926 100644
--- a/spec/ruby/core/string/unpack/h_spec.rb
+++ b/spec/ruby/core/string/unpack/h_spec.rb
@@ -56,8 +56,18 @@ describe "String#unpack with format 'H'" do
     ].should be_computed_by(:unpack, "HHH")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x10".unpack("H\x00H").should == ["0", "1"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x01\x10".unpack("H\x00H").should == ["0", "1"]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x10".unpack("H\x00H")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -121,8 +131,18 @@ describe "String#unpack with format 'h'" do
     ].should be_computed_by(:unpack, "hhh")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x10".unpack("h\x00h").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x01\x10".unpack("h\x00h").should == ["1", "0"]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x10".unpack("h\x00h")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/shared/basic.rb b/spec/ruby/core/string/unpack/shared/basic.rb
index f636f4689f..bb5302edc5 100644
--- a/spec/ruby/core/string/unpack/shared/basic.rb
+++ b/spec/ruby/core/string/unpack/shared/basic.rb
@@ -8,20 +8,6 @@ describe :string_unpack_basic, shared: true do
     d.should_receive(:to_str).and_return("a"+unpack_format)
     "abc".unpack(d).should be_an_instance_of(Array)
   end
-
-  it "raises a TypeError when passed nil" do
-    -> { "abc".unpack(nil) }.should raise_error(TypeError)
-  end
-
-  it "raises a TypeError when passed an Integer" do
-    -> { "abc".unpack(1) }.should raise_error(TypeError)
-  end
-
-  ruby_version_is "3.1" do
-    it "starts unpacking from the given offset" do
-      "abc".unpack("CC", offset: 1).should == [98, 99]
-    end
-  end
 end
 
 describe :string_unpack_no_platform, shared: true do
@@ -32,18 +18,4 @@ describe :string_unpack_no_platform, shared: true do
   it "raises an ArgumentError when the format modifier is '!'" do
     -> { "abcdefgh".unpack(unpack_format("!")) }.should raise_error(ArgumentError)
   end
-
-  ruby_version_is "3.1" do
-    it "raises an ArgumentError when the offset is negative" do
-      -> { "a".unpack("C", offset: -1) }.should raise_error(ArgumentError)
-    end
-
-    it "returns nil if the offset is at the end of the string" do
-      "a".unpack("C", offset: 1).should == [nil]
-    end
-
-    it "raises an ArgumentError when the offset is larget than the string" do
-      -> { "a".unpack("C", offset: 2) }.should raise_error(ArgumentError)
-    end
-  end
 end
diff --git a/spec/ruby/core/string/unpack/shared/float.rb b/spec/ruby/core/string/unpack/shared/float.rb
index 99bd8a3401..ccddf94f99 100644
--- a/spec/ruby/core/string/unpack/shared/float.rb
+++ b/spec/ruby/core/string/unpack/shared/float.rb
@@ -56,9 +56,19 @@ describe :string_unpack_float_le, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
-    array.should == [2.9000000953674316, 1.399999976158142]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      array = "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
+      array.should == [2.9000000953674316, 1.399999976158142]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -123,9 +133,19 @@ describe :string_unpack_float_be, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
-    array.should == [2.9000000953674316, 1.399999976158142]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      array = "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
+      array.should == [2.9000000953674316, 1.399999976158142]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -193,8 +213,18 @@ describe :string_unpack_double_le, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -261,8 +291,18 @@ describe :string_unpack_double_be, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/shared/integer.rb b/spec/ruby/core/string/unpack/shared/integer.rb
index cbaa743683..ba4f149dad 100644
--- a/spec/ruby/core/string/unpack/shared/integer.rb
+++ b/spec/ruby/core/string/unpack/shared/integer.rb
@@ -32,8 +32,18 @@ describe :string_unpack_16bit_le, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abcd".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "abcd".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abcd".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -85,8 +95,18 @@ describe :string_unpack_16bit_be, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "badc".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "badc".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "badc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -139,8 +159,18 @@ describe :string_unpack_32bit_le, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abcdefgh".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "abcdefgh".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abcdefgh".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -193,8 +223,18 @@ describe :string_unpack_32bit_be, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "dcbahgfe".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "dcbahgfe".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "dcbahgfe".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -243,9 +283,19 @@ describe :string_unpack_64bit_le, shared: true do
     "abc".unpack(unpack_format('*')).should == []
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "abcdefghabghefcd".unpack(unpack_format("\000", 2))
-    array.should == [7523094288207667809, 7233738012216484449]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      array = "abcdefghabghefcd".unpack(unpack_format("\000", 2))
+      array.should == [7523094288207667809, 7233738012216484449]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "badc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -305,9 +355,19 @@ describe :string_unpack_64bit_be, shared: true do
     "abc".unpack(unpack_format('*')).should == []
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
-    array.should == [7523094288207667809, 7233738012216484449]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      array = "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
+      array.should == [7523094288207667809, 7233738012216484449]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/shared/unicode.rb b/spec/ruby/core/string/unpack/shared/unicode.rb
index a2b4e142b2..ce1f29fe87 100644
--- a/spec/ruby/core/string/unpack/shared/unicode.rb
+++ b/spec/ruby/core/string/unpack/shared/unicode.rb
@@ -50,8 +50,18 @@ describe :string_unpack_unicode, shared: true do
     "\xc2\x80".unpack("UUUU").should == [0x80]
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x02".unpack("U\x00U").should == [1, 2]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x01\x02".unpack("U\x00U").should == [1, 2]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x02".unpack("U\x00U")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/w_spec.rb b/spec/ruby/core/string/unpack/w_spec.rb
index 011c75f5c4..b213b32921 100644
--- a/spec/ruby/core/string/unpack/w_spec.rb
+++ b/spec/ruby/core/string/unpack/w_spec.rb
@@ -15,8 +15,18 @@ describe "String#unpack with directive 'w'" do
     ].should be_computed_by(:unpack, "w")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x02\x03".unpack("w\x00w").should == [1, 2]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      "\x01\x02\x03".unpack("w\x00w").should == [1, 2]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x02\x03".unpack("w\x00w")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack1_spec.rb b/spec/ruby/core/string/unpack1_spec.rb
index f59bd92d6a..df830916a3 100644
--- a/spec/ruby/core/string/unpack1_spec.rb
+++ b/spec/ruby/core/string/unpack1_spec.rb
@@ -15,16 +15,22 @@ describe "String#unpack1" do
       "ZA".unpack1("B*", offset: 1).should == "01000001"
     end
 
+    it "traits offset as a bytes offset" do
+      "؈".unpack("CC").should == [216, 136]
+      "؈".unpack1("C").should == 216
+      "؈".unpack1("C", offset: 1).should == 136
+    end
+
     it "raises an ArgumentError when the offset is negative" do
-      -> { "a".unpack1("C", offset: -1) }.should raise_error(ArgumentError)
+      -> { "a".unpack1("C", offset: -1) }.should raise_error(ArgumentError, "offset can't be negative")
     end
 
     it "returns nil if the offset is at the end of the string" do
       "a".unpack1("C", offset: 1).should == nil
     end
 
-    it "raises an ArgumentError when the offset is larget than the string" do
-      -> { "a".unpack1("C", offset: 2) }.should raise_error(ArgumentError)
+    it "raises an ArgumentError when the offset is larger than the string bytesize" do
+      -> { "a".unpack1("C", offset: 2) }.should raise_error(ArgumentError, "offset outside of string")
     end
   end
 end
diff --git a/spec/ruby/core/string/unpack_spec.rb b/spec/ruby/core/string/unpack_spec.rb
new file mode 100644
index 0000000000..4ff7d07460
--- /dev/null
+++ b/spec/ruby/core/string/unpack_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+
+describe "String#unpack" do
+  it "raises a TypeError when passed nil" do
+    -> { "abc".unpack(nil) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when passed an Integer" do
+    -> { "abc".unpack(1) }.should raise_error(TypeError)
+  end
+
+  ruby_version_is "3.1" do
+    it "starts unpacking from the given offset" do
+      "abc".unpack("CC", offset: 1).should == [98, 99]
+    end
+
+    it "traits offset as a bytes offset" do
+      "؈".unpack("CC").should == [216, 136]
+      "؈".unpack("CC", offset: 1).should == [136, nil]
+    end
+
+    it "raises an ArgumentError when the offset is negative" do
+      -> { "a".unpack("C", offset: -1) }.should raise_error(ArgumentError, "offset can't be negative")
+    end
+
+    it "returns nil if the offset is at the end of the string" do
+      "a".unpack("C", offset: 1).should == [nil]
+    end
+
+    it "raises an ArgumentError when the offset is larget than the string" do
+      -> { "a".unpack("C", offset: 2) }.should raise_error(ArgumentError, "offset outside of string")
+    end
+  end
+end
\ No newline at end of file
diff --git a/spec/ruby/core/string/upcase_spec.rb b/spec/ruby/core/string/upcase_spec.rb
index 209fe73b6e..5ce7b0b95f 100644
--- a/spec/ruby/core/string/upcase_spec.rb
+++ b/spec/ruby/core/string/upcase_spec.rb
@@ -8,6 +8,10 @@ describe "String#upcase" do
     "hello".upcase.should == "HELLO"
   end
 
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").upcase.encoding.should == Encoding::US_ASCII
+  end
+
   describe "full Unicode case mapping" do
     it "works for all of Unicode with no option" do
       "äöü".upcase.should == "ÄÖÜ"
diff --git a/spec/ruby/core/string/valid_encoding/utf_8_spec.rb b/spec/ruby/core/string/valid_encoding/utf_8_spec.rb
new file mode 100644
index 0000000000..a14c3af830
--- /dev/null
+++ b/spec/ruby/core/string/valid_encoding/utf_8_spec.rb
@@ -0,0 +1,214 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../../spec_helper'
+
+describe "String#valid_encoding? and UTF-8" do
+  def utf8(bytes)
+    bytes.pack("C*").force_encoding("UTF-8")
+  end
+
+  describe "1-byte character" do
+    it "is valid if is in format 0xxxxxxx" do
+      utf8([0b00000000]).valid_encoding?.should == true
+      utf8([0b01111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if is not in format 0xxxxxxx" do
+      utf8([0b10000000]).valid_encoding?.should == false
+      utf8([0b11111111]).valid_encoding?.should == false
+    end
+  end
+
+  describe "2-bytes character" do
+    it "is valid if in format [110xxxxx 10xxxxx]" do
+      utf8([0b11000010, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11000010, 0b10111111]).valid_encoding?.should == true
+
+      utf8([0b11011111, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11011111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 110xxxxx" do
+      utf8([0b00000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11100010, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11000010, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b11000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxxxx10 xx000000] (codepoints < U+007F, that are encoded with the 1-byte format)" do
+      utf8([0b11000000, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11000001, 0b10111111]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11000010, 0b10000000]
+      utf8(bytes[1..1]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11000010, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+
+  describe "3-bytes character" do
+    it "is valid if in format [1110xxxx 10xxxxxx 10xxxxxx]" do
+      utf8([0b11100000, 0b10100000, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11100000, 0b10100000, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11100000, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11101111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 1110xxxx" do
+      utf8([0b00000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11100000, 0b00100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b01100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b11100000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the third byte is not in format 10xxxxxx" do
+      utf8([0b11100000, 0b10100000, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b01000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxx0000 xx100000 xx000000] (codepoints < U+07FF that are encoded with the 2-byte format)" do
+      utf8([0b11100000, 0b10010000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10001000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000100, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000001, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if in range [xxxx1101 xx100000 xx000000] - [xxxx1101 xx111111 xx111111] (codepoints U+D800 - U+DFFF)" do
+      utf8([0b11101101, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11101101, 0b10100000, 0b10000001]).valid_encoding?.should == false
+      utf8([0b11101101, 0b10111111, 0b10111111]).valid_encoding?.should == false
+
+      utf8([0b11101101, 0b10011111, 0b10111111]).valid_encoding?.should == true # lower boundary - 1
+      utf8([0b11101110, 0b10000000, 0b10000000]).valid_encoding?.should == true # upper boundary + 1
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8(bytes[2..3]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8([bytes[0], bytes[2]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second and the third bytes are missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+
+  describe "4-bytes character" do
+    it "is valid if in format [11110xxx 10xxxxxx 10xxxxxx 10xxxxxx]" do
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10010000, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10111111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110100, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 11110xxx" do
+      utf8([0b11100000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11010000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b00010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b01010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b11010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the third byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b10010000, 0b00000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b01000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10010000, 0b11000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the forth byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b11000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxxx000 xx001000 xx000000 xx000000] (codepoint < U+10000)" do
+      utf8([0b11110000, 0b10000111, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000110, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000101, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000100, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000011, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000010, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000001, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is greater than [xxxxx100 xx001111 xx111111 xx111111] (codepoint > U+10FFFF)" do
+      utf8([0b11110100, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110100, 0b10100000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110100, 0b10110000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+
+      utf8([0b11110101, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11110110, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11110111, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8(bytes[1..3]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8([bytes[0], bytes[2], bytes[3]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second and the third bytes are missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8([bytes[0], bytes[3]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second, the third and the fourth bytes are missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/struct/values_at_spec.rb b/spec/ruby/core/struct/values_at_spec.rb
index e7d287cba2..5e5a496600 100644
--- a/spec/ruby/core/struct/values_at_spec.rb
+++ b/spec/ruby/core/struct/values_at_spec.rb
@@ -1,16 +1,59 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+# Should be synchronized with core/array/values_at_spec.rb
 describe "Struct#values_at" do
-  it "returns an array of values" do
+  before do
     clazz = Struct.new(:name, :director, :year)
-    movie = clazz.new('Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002)
-    movie.values_at(0, 1).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park']
-    movie.values_at(0..2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002]
+    @movie = clazz.new('Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002)
+  end
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      @movie.values_at(0, 1).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park']
+    end
+
+    it "raises IndexError if any of integers is out of range" do
+      -> { @movie.values_at(3) }.should raise_error(IndexError, "offset 3 too large for struct(size:3)")
+      -> { @movie.values_at(-4) }.should raise_error(IndexError, "offset -4 too small for struct(size:3)")
+    end
+  end
+
+  context "when passed an integer Range" do
+    it "returns an array containing each value given by the elements of the range" do
+      @movie.values_at(0..2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002]
+    end
+
+    it "fills with nil values for range elements larger than the structure" do
+      @movie.values_at(0..3).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, nil]
+    end
+
+    it "raises RangeError if any element of the range is negative and out of range" do
+      -> { @movie.values_at(-4..3) }.should raise_error(RangeError, "-4..3 out of range")
+    end
+
+    it "supports endless Range" do
+      @movie.values_at(0..).should == ["Sympathy for Mr. Vengeance", "Chan-wook Park", 2002]
+    end
+
+    it "supports beginningless Range" do
+      @movie.values_at(..2).should == ["Sympathy for Mr. Vengeance", "Chan-wook Park", 2002]
+    end
+  end
+
+  it "supports multiple integer Ranges" do
+    @movie.values_at(0..2, 1..2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, 'Chan-wook Park', 2002]
+  end
+
+  it "supports mixing integer Ranges and Integers" do
+    @movie.values_at(0..2, 2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, 2002]
+  end
+
+  it "returns a new empty Array if no arguments given" do
+    @movie.values_at().should == []
   end
 
   it "fails when passed unsupported types" do
-    car = StructClasses::Car.new('Ford', 'Ranger')
-    -> { car.values_at('make') }.should raise_error(TypeError)
+    -> { @movie.values_at('make') }.should raise_error(TypeError, "no implicit conversion of String into Integer")
   end
 end
diff --git a/spec/ruby/core/symbol/shared/id2name.rb b/spec/ruby/core/symbol/shared/id2name.rb
index 47f97bd332..d012b7634e 100644
--- a/spec/ruby/core/symbol/shared/id2name.rb
+++ b/spec/ruby/core/symbol/shared/id2name.rb
@@ -6,4 +6,11 @@ describe :symbol_id2name, shared: true do
     :@ruby.send(@method).should == "@ruby"
     :@@ruby.send(@method).should == "@@ruby"
   end
+
+  it "returns a String in the same encoding as self" do
+    string = "ruby".encode("US-ASCII")
+    symbol = string.to_sym
+
+    symbol.send(@method).encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/time/at_spec.rb b/spec/ruby/core/time/at_spec.rb
index 74b1962a95..0459589f01 100644
--- a/spec/ruby/core/time/at_spec.rb
+++ b/spec/ruby/core/time/at_spec.rb
@@ -251,6 +251,22 @@ describe "Time.at" do
       time.to_i.should == @epoch_time
     end
 
+    it "could be UTC offset as a 'UTC' String" do
+      time = Time.at(@epoch_time, in: "UTC")
+
+      time.utc_offset.should == 0
+      time.zone.should == "UTC"
+      time.to_i.should == @epoch_time
+    end
+
+    it "could be UTC offset as a military zone A-Z" do
+      time = Time.at(@epoch_time, in: "B")
+
+      time.utc_offset.should == 3600 * 2
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
+    end
+
     it "could be a timezone object" do
       zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
       time = Time.at(@epoch_time, in: zone)
diff --git a/spec/ruby/core/time/localtime_spec.rb b/spec/ruby/core/time/localtime_spec.rb
index 2975e112d0..609b6532a1 100644
--- a/spec/ruby/core/time/localtime_spec.rb
+++ b/spec/ruby/core/time/localtime_spec.rb
@@ -29,10 +29,10 @@ describe "Time#localtime" do
       time.localtime.should equal(time)
     end
 
-    it "raises a RuntimeError if the time has a different time zone" do
+    it "raises a FrozenError if the time has a different time zone" do
       time = Time.gm(2007, 1, 9, 12, 0, 0)
       time.freeze
-      -> { time.localtime }.should raise_error(RuntimeError)
+      -> { time.localtime }.should raise_error(FrozenError)
     end
   end
 
@@ -79,6 +79,18 @@ describe "Time#localtime" do
     t.utc_offset.should == -3600
   end
 
+  it "returns a Time with a UTC offset specified as UTC" do
+    t = Time.new(2007, 1, 9, 12, 0, 0, 3600)
+    t.localtime("UTC")
+    t.utc_offset.should == 0
+  end
+
+  it "returns a Time with a UTC offset specified as A-Z military zone" do
+    t = Time.new(2007, 1, 9, 12, 0, 0, 3600)
+    t.localtime("B")
+    t.utc_offset.should == 3600 * 2
+  end
+
   platform_is_not :windows do
     it "changes the timezone according to the set one" do
       t = Time.new(2005, 2, 27, 22, 50, 0, -3600)
diff --git a/spec/ruby/core/time/new_spec.rb b/spec/ruby/core/time/new_spec.rb
index aabf28e712..727fdf92c2 100644
--- a/spec/ruby/core/time/new_spec.rb
+++ b/spec/ruby/core/time/new_spec.rb
@@ -58,6 +58,32 @@ describe "Time.new with a utc_offset argument" do
     Time.new(2000, 1, 1, 0, 0, 0, "-04:10:43").utc_offset.should == -15043
   end
 
+  ruby_bug '#13669', '3.0'...'3.1' do
+    it "returns a Time with a UTC offset specified as +HH" do
+      Time.new(2000, 1, 1, 0, 0, 0, "+05").utc_offset.should == 3600 * 5
+    end
+
+    it "returns a Time with a UTC offset specified as -HH" do
+      Time.new(2000, 1, 1, 0, 0, 0, "-05").utc_offset.should == -3600 * 5
+    end
+
+    it "returns a Time with a UTC offset specified as +HHMM" do
+      Time.new(2000, 1, 1, 0, 0, 0, "+0530").utc_offset.should == 19800
+    end
+
+    it "returns a Time with a UTC offset specified as -HHMM" do
+      Time.new(2000, 1, 1, 0, 0, 0, "-0530").utc_offset.should == -19800
+    end
+
+    it "returns a Time with a UTC offset specified as +HHMMSS" do
+      Time.new(2000, 1, 1, 0, 0, 0, "+053037").utc_offset.should == 19837
+    end
+
+    it "returns a Time with a UTC offset specified as -HHMMSS" do
+      Time.new(2000, 1, 1, 0, 0, 0, "-053037").utc_offset.should == -19837
+    end
+  end
+
   describe "with an argument that responds to #to_str" do
     it "coerces using #to_str" do
       o = mock('string')
@@ -66,6 +92,57 @@ describe "Time.new with a utc_offset argument" do
     end
   end
 
+  it "returns a Time with UTC offset specified as UTC" do
+    Time.new(2000, 1, 1, 0, 0, 0, "UTC").utc_offset.should == 0
+  end
+
+  it "returns a Time with UTC offset specified as a single letter military timezone" do
+    [
+      ["A", 3600],
+      ["B", 3600 * 2],
+      ["C", 3600 * 3],
+      ["D", 3600 * 4],
+      ["E", 3600 * 5],
+      ["F", 3600 * 6],
+      ["G", 3600 * 7],
+      ["H", 3600 * 8],
+      ["I", 3600 * 9],
+      # J is not supported
+      ["K", 3600 * 10],
+      ["L", 3600 * 11],
+      ["M", 3600 * 12],
+      ["N", 3600 * -1],
+      ["O", 3600 * -2],
+      ["P", 3600 * -3],
+      ["Q", 3600 * -4],
+      ["R", 3600 * -5],
+      ["S", 3600 * -6],
+      ["T", 3600 * -7],
+      ["U", 3600 * -8],
+      ["V", 3600 * -9],
+      ["W", 3600 * -10],
+      ["X", 3600 * -11],
+      ["Y", 3600 * -12],
+      ["Z", 0]
+    ].each do |letter, offset|
+      Time.new(2000, 1, 1, 0, 0, 0, letter).utc_offset.should == offset
+    end
+  end
+
+  ruby_version_is ""..."3.1" do
+    it "raises ArgumentError if the string argument is J" do
+      message = '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset'
+      -> { Time.new(2000, 1, 1, 0, 0, 0, "J") }.should raise_error(ArgumentError, message)
+    end
+  end
+
+  ruby_version_is "3.1" do
+    it "raises ArgumentError if the string argument is J" do
+      message = '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: J'
+      -> { Time.new(2000, 1, 1, 0, 0, 0, "J") }.should raise_error(ArgumentError, message)
+    end
+  end
+
   it "returns a local Time if the argument is nil" do
     with_timezone("PST", -8) do
       t = Time.new(2000, 1, 1, 0, 0, 0, nil)
@@ -93,7 +170,12 @@ describe "Time.new with a utc_offset argument" do
   end
 
   it "raises ArgumentError if the String argument is not in an ASCII-compatible encoding" do
-    -> { Time.new(2000, 1, 1, 0, 0, 0, "-04:10".encode("UTF-16LE")) }.should raise_error(ArgumentError)
+    # Don't check exception message - it was changed in previous CRuby versions:
+    # - "string contains null byte"
+    # - '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset'
+    -> {
+      Time.new(2000, 1, 1, 0, 0, 0, "-04:10".encode("UTF-16LE"))
+    }.should raise_error(ArgumentError)
   end
 
   it "raises ArgumentError if the argument represents a value less than or equal to -86400 seconds" do
@@ -106,19 +188,9 @@ describe "Time.new with a utc_offset argument" do
     -> { Time.new(2000, 1, 1, 0, 0, 0, 86400) }.should raise_error(ArgumentError)
   end
 
-  it "raises ArgumentError if the seconds argument is negative" do
-    -> { Time.new(2000, 1, 1, 0, 0, -1) }.should raise_error(ArgumentError)
-  end
-
   it "raises ArgumentError if the utc_offset argument is greater than or equal to 10e9" do
     -> { Time.new(2000, 1, 1, 0, 0, 0, 1000000000) }.should raise_error(ArgumentError)
   end
-
-  it "raises ArgumentError if the month is greater than 12" do
-    # For some reason MRI uses a different message for month in 13-15 and month>=16
-    -> { Time.new(2000, 13, 1, 0, 0, 0, "+01:00") }.should raise_error(ArgumentError, /(mon|argument) out of range/)
-    -> { Time.new(2000, 16, 1, 0, 0, 0, "+01:00") }.should raise_error(ArgumentError, "argument out of range")
-  end
 end
 
 describe "Time.new with a timezone argument" do
diff --git a/spec/ruby/core/time/shared/gmtime.rb b/spec/ruby/core/time/shared/gmtime.rb
index 5ed64c2ab6..bae19da462 100644
--- a/spec/ruby/core/time/shared/gmtime.rb
+++ b/spec/ruby/core/time/shared/gmtime.rb
@@ -22,11 +22,11 @@ describe :time_gmtime, shared: true do
       time.send(@method).should equal(time)
     end
 
-    it "raises a RuntimeError if the time is not UTC" do
+    it "raises a FrozenError if the time is not UTC" do
       with_timezone("CST", -6) do
         time = Time.now
         time.freeze
-        -> { time.send(@method) }.should raise_error(RuntimeError)
+        -> { time.send(@method) }.should raise_error(FrozenError)
       end
     end
   end
diff --git a/spec/ruby/core/time/shared/time_params.rb b/spec/ruby/core/time/shared/time_params.rb
index 63d0dbc120..b6a6c88c8e 100644
--- a/spec/ruby/core/time/shared/time_params.rb
+++ b/spec/ruby/core/time/shared/time_params.rb
@@ -145,9 +145,10 @@ describe :time_params, shared: true do
   end
 
   it "raises an ArgumentError for out of range month" do
+    # For some reason MRI uses a different message for month in 13-15 and month>=16
     -> {
-      Time.send(@method, 2008, 13, 31, 23, 59, 59)
-    }.should raise_error(ArgumentError)
+      Time.send(@method, 2008, 16, 31, 23, 59, 59)
+    }.should raise_error(ArgumentError, /(mon|argument) out of range/)
   end
 
   it "raises an ArgumentError for out of range day" do
@@ -169,9 +170,13 @@ describe :time_params, shared: true do
   end
 
   it "raises an ArgumentError for out of range second" do
+    # For some reason MRI uses different messages for seconds 61-63 and seconds >= 64
     -> {
       Time.send(@method, 2008, 12, 31, 23, 59, 61)
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /(sec|argument) out of range/)
+    -> {
+      Time.send(@method, 2008, 12, 31, 23, 59, -1)
+    }.should raise_error(ArgumentError, "argument out of range")
   end
 
   it "raises ArgumentError when given 9 arguments" do
diff --git a/spec/ruby/core/time/strftime_spec.rb b/spec/ruby/core/time/strftime_spec.rb
index c133e22008..4cb300c916 100644
--- a/spec/ruby/core/time/strftime_spec.rb
+++ b/spec/ruby/core/time/strftime_spec.rb
@@ -52,10 +52,42 @@ describe "Time#strftime" do
 
   ruby_version_is "3.1" do
     it "supports RFC 3339 UTC for unknown offset local time, -0000, as %-z" do
-      @time.strftime("%z").should == "+0000"
-      @time.strftime("%-z").should == "-0000"
-      @time.strftime("%-:z").should == "-00:00"
-      @time.strftime("%-::z").should == "-00:00:00"
+      time = Time.gm(2022)
+
+      time.strftime("%z").should == "+0000"
+      time.strftime("%-z").should == "-0000"
+      time.strftime("%-:z").should == "-00:00"
+      time.strftime("%-::z").should == "-00:00:00"
+    end
+
+    it "applies '-' flag to UTC time" do
+      time = Time.utc(2022)
+      time.strftime("%-z").should == "-0000"
+
+      time = Time.gm(2022)
+      time.strftime("%-z").should == "-0000"
+
+      time = Time.new(2022, 1, 1, 0, 0, 0, "Z")
+      time.strftime("%-z").should == "-0000"
+
+      time = Time.new(2022, 1, 1, 0, 0, 0, "-00:00")
+      time.strftime("%-z").should == "-0000"
+
+      time = Time.new(2022, 1, 1, 0, 0, 0, "+03:00").utc
+      time.strftime("%-z").should == "-0000"
+    end
+
+    it "ignores '-' flag for non-UTC time" do
+      time = Time.new(2022, 1, 1, 0, 0, 0, "+03:00")
+      time.strftime("%-z").should == "+0300"
+    end
+
+    it "works correctly with width, _ and 0 flags, and :" do
+      Time.now.utc.strftime("%-_10z").should == "      -000"
+      Time.now.utc.strftime("%-10z").should == "-000000000"
+      Time.now.utc.strftime("%-010:z").should == "-000000:00"
+      Time.now.utc.strftime("%-_10:z").should == "     -0:00"
+      Time.now.utc.strftime("%-_10::z").should == "  -0:00:00"
     end
   end
 end
diff --git a/spec/ruby/core/time/utc_spec.rb b/spec/ruby/core/time/utc_spec.rb
index 74c17a93d1..809accc809 100644
--- a/spec/ruby/core/time/utc_spec.rb
+++ b/spec/ruby/core/time/utc_spec.rb
@@ -4,8 +4,45 @@ require_relative 'shared/gmtime'
 require_relative 'shared/time_params'
 
 describe "Time#utc?" do
-  it "returns true if time represents a time in UTC (GMT)" do
-    Time.now.should_not.utc?
+  it "returns true only if time represents a time in UTC (GMT)" do
+    Time.now.utc?.should == false
+    Time.now.utc.utc?.should == true
+  end
+
+  it "treats time as UTC what was created in different ways" do
+    Time.now.utc.utc?.should == true
+    Time.now.gmtime.utc?.should == true
+    Time.now.getgm.utc?.should == true
+    Time.now.getutc.utc?.should == true
+    Time.utc(2022).utc?.should == true
+  end
+
+  it "does treat time with 'UTC' offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "UTC").utc?.should == true
+    Time.now.localtime("UTC").utc?.should == true
+    Time.at(Time.now, in: 'UTC').utc?.should == true
+  end
+
+  it "does treat time with Z offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "Z").utc?.should == true
+    Time.now.localtime("Z").utc?.should == true
+    Time.at(Time.now, in: 'Z').utc?.should == true
+  end
+
+  ruby_version_is "3.1" do
+    it "does treat time with -00:00 offset as UTC" do
+      Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc?.should == true
+      Time.now.localtime("-00:00").utc?.should == true
+      Time.at(Time.now, in: '-00:00').utc?.should == true
+    end
+  end
+
+  it "does not treat time with +00:00 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "+00:00").utc?.should == false
+  end
+
+  it "does not treat time with 0 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, 0).utc?.should == false
   end
 end
 
diff --git a/spec/ruby/core/time/zone_spec.rb b/spec/ruby/core/time/zone_spec.rb
index 907ccf9f4b..cbb0977f24 100644
--- a/spec/ruby/core/time/zone_spec.rb
+++ b/spec/ruby/core/time/zone_spec.rb
@@ -52,14 +52,28 @@ describe "Time#zone" do
     end
 
     it "doesn't raise errors for a Time with a fixed offset" do
-      -> {
-        Time.new(2001, 1, 1, 0, 0, 0, "+05:00").zone
-      }.should_not raise_error
+      Time.new(2001, 1, 1, 0, 0, 0, "+05:00").zone.should == nil
     end
   end
 
   it "returns UTC when called on a UTC time" do
     Time.now.utc.zone.should == "UTC"
+    Time.now.gmtime.zone.should == "UTC"
+    Time.now.getgm.zone.should == "UTC"
+    Time.now.getutc.zone.should == "UTC"
+    Time.utc(2022).zone.should == "UTC"
+    Time.new(2022, 1, 1, 0, 0, 0, "UTC").zone.should == "UTC"
+    Time.new(2022, 1, 1, 0, 0, 0, "Z").zone.should == "UTC"
+    Time.now.localtime("UTC").zone.should == "UTC"
+    Time.now.localtime("Z").zone.should == "UTC"
+    Time.at(Time.now, in: 'UTC').zone.should == "UTC"
+    Time.at(Time.now, in: 'Z').zone.should == "UTC"
+
+    ruby_version_is "3.1" do
+      Time.new(2022, 1, 1, 0, 0, 0, "-00:00").zone.should == "UTC"
+      Time.now.localtime("-00:00").zone.should == "UTC"
+      Time.at(Time.now, in: '-00:00').zone.should == "UTC"
+    end
   end
 
   platform_is_not :aix, :windows do
diff --git a/spec/ruby/core/tracepoint/inspect_spec.rb b/spec/ruby/core/tracepoint/inspect_spec.rb
index a07b626212..151a08e7b4 100644
--- a/spec/ruby/core/tracepoint/inspect_spec.rb
+++ b/spec/ruby/core/tracepoint/inspect_spec.rb
@@ -16,6 +16,15 @@ describe 'TracePoint#inspect' do
     TracePoint.new(:line) {}.inspect.should == '#<TracePoint:disabled>'
   end
 
+  it "shows only whether it's enabled when outside the TracePoint handler" do
+    trace = TracePoint.new(:line) {}
+    trace.enable
+
+    trace.inspect.should == '#<TracePoint:enabled>'
+
+    trace.disable
+  end
+
   it 'returns a String showing the event, path and line' do
     inspect = nil
     line = nil