def test_defaultIsSuccessful(self):
        """
        The test case type can be instantiated with no arguments, run, and
        reported as being successful.
        """
        test = self.__class__()
        test.run(self.result)
        self.assertSuccessful(test, self.result)

        The test case type can be instantiated with no arguments, run, and
        reported as being successful.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_tests.py