def assertSuccessful(self, test, result):
        """
        Utility function -- assert there is one success and the state is
        plausible
        """
        self.assertEqual(result.successes, 1)
        self.assertEqual(result.failures, [])
        self.assertEqual(result.errors, [])
        self.assertEqual(result.expectedFailures, [])
        self.assertEqual(result.unexpectedSuccesses, [])
        self.assertEqual(result.skips, [])

        Utility function -- assert there is one success and the state is
        plausible
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_tests.py