ot null, we iterate over properties to do a deeper comparison..
                        for(var prop in expectedResponse){
                          if (expectedResponse[prop] instanceof Array) {
                            assert_array_equals(expectedResponse[prop], xhr.response[prop])
                          }else{
                            assert_equals(expectedResponse[prop], xhr.response[prop])
                          }
                        }
                    }else{
                        