Add spec for `Warning[:performance]`

[Feature #19538]

NEWS.md

@@ -7,6 +7,12 @@ Note that each entry is kept to a minimum, see links for details.
 
 ## Language changes
 
+## Command line options
+
+* A new `performance` warning category was introduced.
+  They are not displayed by default even in verbose mode.
+  Turn them on with `-W:performance` or `Warning[:performance] = true`. [[Feature #19538]]
+
 ## Core classes updates
 
 Note: We're only listing outstanding class updates.
@@ -79,5 +85,7 @@ changelog for details of the default gems or bundled gems.
 ## JIT
 
 [Bug #19150]:     https://bugs.ruby-lang.org/issues/19150
+[Feature #18498]: https://bugs.ruby-lang.org/issues/18498
 [Feature #19314]: https://bugs.ruby-lang.org/issues/19314
 [Feature #19347]: https://bugs.ruby-lang.org/issues/19347
+[Feature #19538]: https://bugs.ruby-lang.org/issues/19538

spec/ruby/core/warning/element_reference_spec.rb

@@ -8,6 +8,13 @@ describe "Warning.[]" do
     end
   end
 
+  ruby_version_is '3.3' do
+    it "returns default values for :performance category" do
+      ruby_exe('p Warning[:performance]').chomp.should == "false"
+      ruby_exe('p Warning[:performance]', options: "-w").chomp.should == "false"
+    end
+  end
+
   it "raises for unknown category" do
     -> { Warning[:noop] }.should raise_error(ArgumentError, /unknown category: noop/)
   end