/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/ is in ruby-shoulda-matchers 1.0.0~beta2-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/assign_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/redirect_to_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/render_template_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/respond_with_content_type_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/respond_with_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/route_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/set_session_matcher.rb
/usr/lib/ruby/vendor_ruby/shoulda/matchers/action_controller/set_the_flash_matcher.rb