def test_successfulIsReported(self):
        """
        Test that when a successful test is run, it is reported as a success,
        and not as any other kind of result.
        """
        test = self.__class__('test_successful')
        test.run(self.result)
        self.assertSuccessful(test, self.result)

        Test that when a successful test is run, it is reported as a success,
        and not as any other kind of result.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_tests.py