Warning[:performance] is new in Ruby 3.3. Thanks, CI!

Author: ParadoxV5

Rakefile

@@ -7,5 +7,7 @@ require 'minitest/test_task'
 # * test:slow     : run tests and reports the slowest 25
 Minitest::TestTask.create do |t|
   t.extra_args << '-Werror' # Raise exceptions for warnings: https://github.com/minitest/minitest/commit/f0f17b9
-  t.test_prelude = 'Warning[:performance] = true' # … including `performance` warnings which are off even with `-w`
+  if RUBY_VERSION > '3.3'
+    t.test_prelude = 'Warning[:performance] = true' # … including `performance` warnings which are off even with `-w`
+  end
 end