/usr/lib/ruby/ is in ruby-shoulda-matchers 1.0.0~beta2-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/shoulda/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/version.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/integrations/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/integrations/test_unit.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/integrations/rspec.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/assertion_error.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validation_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validate_uniqueness_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validate_presence_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validate_numericality_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validate_format_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/validate_acceptance_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/helpers.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/have_readonly_attribute_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/have_db_index_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/have_db_column_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/ensure_length_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/ensure_inclusion_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/association_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/allow_value_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record/allow_mass_assignment_of_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/active_record.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_mailer/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_mailer/have_sent_email.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_mailer.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/set_the_flash_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/set_session_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/route_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/respond_with_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/respond_with_content_type_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/render_with_layout_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/render_template_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/redirect_to_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/filter_param_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/assign_to_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers.rb
/usr/lib/ruby/vendor_ruby/shoulda-matchers.rb