merge revision(s) cd5e6cc0ea48353c88d921b885b552dc76da255c,bbf54ec334fe2edd7669a944d88d17efde49a412: [Backport #19307]

	Update to ruby/mspec@fef9b81

	---
	 spec/mspec/tool/tag_from_output.rb | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

	Update to ruby/spec@9d69b95

	---
	 spec/ruby/core/array/keep_if_spec.rb               |   1 +
	 spec/ruby/core/array/pack/c_spec.rb                |  14 +-
	 spec/ruby/core/array/pack/shared/basic.rb          |  40 ++++
	 spec/ruby/core/array/pack/shared/float.rb          |  66 ++++++-
	 spec/ruby/core/array/pack/shared/integer.rb        |  96 +++++++--
	 spec/ruby/core/array/pack/shared/numeric_basic.rb  |  10 +-
	 spec/ruby/core/array/pack/shared/unicode.rb        |  14 +-
	 spec/ruby/core/array/pack/w_spec.rb                |  14 +-
	 spec/ruby/core/array/shared/unshift.rb             |  18 ++
	 spec/ruby/core/array/values_at_spec.rb             |   1 +
	 spec/ruby/core/array/zip_spec.rb                   |   6 +
	 spec/ruby/core/class/subclasses_spec.rb            |  22 +++
	 spec/ruby/core/dir/home_spec.rb                    |  44 +++--
	 spec/ruby/core/dir/mkdir_spec.rb                   |  18 +-
	 spec/ruby/core/enumerable/zip_spec.rb              |   5 +
	 spec/ruby/core/float/comparison_spec.rb            |  35 ++--
	 spec/ruby/core/float/divmod_spec.rb                |   2 +-
	 spec/ruby/core/float/gt_spec.rb                    |  21 ++
	 spec/ruby/core/float/gte_spec.rb                   |  21 ++
	 spec/ruby/core/float/lt_spec.rb                    |  21 ++
	 spec/ruby/core/float/lte_spec.rb                   |  21 ++
	 spec/ruby/core/float/shared/equal.rb               |  21 ++
	 spec/ruby/core/io/gets_spec.rb                     |   4 +
	 spec/ruby/core/io/lineno_spec.rb                   |   9 +-
	 spec/ruby/core/io/new_spec.rb                      |   2 +
	 spec/ruby/core/io/readline_spec.rb                 |   4 +
	 spec/ruby/core/io/readlines_spec.rb                |   4 +
	 spec/ruby/core/io/shared/each.rb                   |   4 +
	 spec/ruby/core/io/shared/new.rb                    |   2 +
	 spec/ruby/core/io/shared/pos.rb                    |   8 +-
	 spec/ruby/core/io/shared/readlines.rb              |   4 +
	 spec/ruby/core/io/sysseek_spec.rb                  |   2 +-
	 spec/ruby/core/kernel/shared/load.rb               |  31 ++-
	 spec/ruby/core/kernel/singleton_class_spec.rb      |   2 +
	 spec/ruby/core/marshal/dump_spec.rb                |  45 ++++-
	 spec/ruby/core/marshal/fixtures/classes.rb         |   4 +
	 spec/ruby/core/matchdata/values_at_spec.rb         |  73 ++++++-
	 spec/ruby/core/module/fixtures/classes.rb          |   1 +
	 spec/ruby/core/module/include_spec.rb              |   4 +-
	 spec/ruby/core/module/prepend_spec.rb              |  12 ++
	 .../ruby/core/objectspace/define_finalizer_spec.rb |  22 +++
	 spec/ruby/core/process/constants_spec.rb           |   1 +
	 spec/ruby/core/process/detach_spec.rb              |  29 +++
	 spec/ruby/core/process/spawn_spec.rb               |  10 +
	 spec/ruby/core/process/times_spec.rb               |   2 +-
	 spec/ruby/core/queue/initialize_spec.rb            |  13 +-
	 spec/ruby/core/refinement/import_methods_spec.rb   |  34 ++++
	 spec/ruby/core/refinement/include_spec.rb          |  27 +++
	 spec/ruby/core/refinement/prepend_spec.rb          |  27 +++
	 spec/ruby/core/regexp/initialize_spec.rb           |   2 +-
	 spec/ruby/core/signal/trap_spec.rb                 |  12 ++
	 spec/ruby/core/string/byteslice_spec.rb            |   6 +
	 spec/ruby/core/string/capitalize_spec.rb           |   4 +
	 spec/ruby/core/string/chars_spec.rb                |   7 +-
	 spec/ruby/core/string/chomp_spec.rb                |   4 +
	 spec/ruby/core/string/chop_spec.rb                 |   4 +
	 spec/ruby/core/string/clone_spec.rb                |   4 +
	 spec/ruby/core/string/delete_prefix_spec.rb        |   4 +
	 spec/ruby/core/string/delete_spec.rb               |   4 +
	 spec/ruby/core/string/delete_suffix_spec.rb        |   4 +
	 spec/ruby/core/string/downcase_spec.rb             |   4 +
	 spec/ruby/core/string/dump_spec.rb                 |  10 +-
	 spec/ruby/core/string/dup_spec.rb                  |   4 +
	 spec/ruby/core/string/lines_spec.rb                |   1 -
	 spec/ruby/core/string/reverse_spec.rb              |   4 +
	 spec/ruby/core/string/scan_spec.rb                 |   6 +
	 spec/ruby/core/string/scrub_spec.rb                |  10 +
	 spec/ruby/core/string/shared/each_line.rb          |   6 +
	 spec/ruby/core/string/shared/partition.rb          |  15 ++
	 spec/ruby/core/string/shared/slice.rb              |  13 +-
	 spec/ruby/core/string/shared/strip.rb              |   4 +
	 spec/ruby/core/string/shared/succ.rb               |   4 +
	 spec/ruby/core/string/split_spec.rb                |  17 +-
	 spec/ruby/core/string/squeeze_spec.rb              |   5 +
	 spec/ruby/core/string/swapcase_spec.rb             |   4 +
	 spec/ruby/core/string/undump_spec.rb               |   2 +-
	 spec/ruby/core/string/unpack/b_spec.rb             |  28 ++-
	 spec/ruby/core/string/unpack/c_spec.rb             |  14 +-
	 spec/ruby/core/string/unpack/h_spec.rb             |  28 ++-
	 spec/ruby/core/string/unpack/shared/basic.rb       |  28 ---
	 spec/ruby/core/string/unpack/shared/float.rb       |  60 +++++-
	 spec/ruby/core/string/unpack/shared/integer.rb     |  88 +++++++--
	 spec/ruby/core/string/unpack/shared/unicode.rb     |  14 +-
	 spec/ruby/core/string/unpack/w_spec.rb             |  14 +-
	 spec/ruby/core/string/unpack1_spec.rb              |  12 +-
	 spec/ruby/core/string/unpack_spec.rb               |  34 ++++
	 spec/ruby/core/string/upcase_spec.rb               |   4 +
	 spec/ruby/core/string/valid_encoding/utf_8_spec.rb | 214 +++++++++++++++++++++
	 spec/ruby/core/struct/values_at_spec.rb            |  55 +++++-
	 spec/ruby/core/symbol/shared/id2name.rb            |   7 +
	 spec/ruby/core/time/at_spec.rb                     |  16 ++
	 spec/ruby/core/time/localtime_spec.rb              |  16 +-
	 spec/ruby/core/time/new_spec.rb                    |  94 +++++++--
	 spec/ruby/core/time/shared/gmtime.rb               |   4 +-
	 spec/ruby/core/time/shared/time_params.rb          |  11 +-
	 spec/ruby/core/time/strftime_spec.rb               |  40 +++-
	 spec/ruby/core/time/utc_spec.rb                    |  41 +++-
	 spec/ruby/core/time/zone_spec.rb                   |  20 +-
	 spec/ruby/core/tracepoint/inspect_spec.rb          |   9 +
	 spec/ruby/fixtures/code/load_wrap_fixture.rb       |  12 ++
	 spec/ruby/fixtures/code/wrap_fixture.rb            |   9 -
	 spec/ruby/language/case_spec.rb                    |   4 +-
	 .../ruby/language/regexp/character_classes_spec.rb |   5 +
	 spec/ruby/library/coverage/running_spec.rb         |  20 ++
	 spec/ruby/library/date/civil_spec.rb               |   7 +-
	 spec/ruby/library/objectspace/fixtures/trace.rb    |   5 +
	 spec/ruby/library/objectspace/trace_spec.rb        |  15 ++
	 spec/ruby/library/openssl/x509/name/verify_spec.rb |   4 +-
	 spec/ruby/library/stringio/initialize_spec.rb      |  85 ++++++++
	 spec/ruby/library/stringio/new_spec.rb             |   8 +
	 spec/ruby/library/stringio/shared/write.rb         |  22 +++
	 spec/ruby/optional/capi/ext/io_spec.c              |  43 +++++
	 spec/ruby/optional/capi/io_spec.rb                 |  15 ++
	 spec/ruby/shared/rational/Rational.rb              |  48 ++---
	 114 files changed, 1963 insertions(+), 245 deletions(-)
	 create mode 100644 spec/ruby/core/marshal/fixtures/classes.rb
	 create mode 100644 spec/ruby/core/refinement/import_methods_spec.rb
	 create mode 100644 spec/ruby/core/refinement/include_spec.rb
	 create mode 100644 spec/ruby/core/refinement/prepend_spec.rb
	 create mode 100644 spec/ruby/core/string/unpack_spec.rb
	 create mode 100644 spec/ruby/core/string/valid_encoding/utf_8_spec.rb
	 create mode 100644 spec/ruby/fixtures/code/load_wrap_fixture.rb
	 delete mode 100644 spec/ruby/fixtures/code/wrap_fixture.rb
	 create mode 100644 spec/ruby/library/coverage/running_spec.rb
	 create mode 100644 spec/ruby/library/objectspace/fixtures/trace.rb
	 create mode 100644 spec/ruby/library/objectspace/trace_spec.rb
	 create mode 100644 spec/ruby/library/stringio/new_spec.rb

8 files changed, 215 insertions, 27 deletions

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