/usr/lib/ruby/ is in ruby-minitest-utils 0.2.4+debian-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/minitest/
/usr/lib/ruby/vendor_ruby/minitest/utils_plugin.rb
/usr/lib/ruby/vendor_ruby/minitest/utils.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/
/usr/lib/ruby/vendor_ruby/minitest/utils/version.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/extension.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/reporter.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/webmock.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/locale.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/database_cleaner.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/factory_girl.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/rails/capybara.rb
/usr/lib/ruby/vendor_ruby/minitest/utils/test_notifier_reporter.rb