Flunk makes a lot more sense, doesnt it (hat tip @tenderlove)

actionpack/lib/action_dispatch/testing/assertions/response.rb

@@ -42,7 +42,7 @@ def assert_response(type, message = nil)
         elsif type.is_a?(Symbol) && @response.response_code == Rack::Utils::SYMBOL_TO_STATUS_CODE[type]
           assert_block("") { true } # to count the assertion
         else
-          assert(false, build_message(message, "Expected response to be a <?>, but was <?>", type, @response.response_code))
+          flunk(build_message(message, "Expected response to be a <?>, but was <?>", type, @response.response_code))
         end
       end