def test_startSuccessStop(self):
        """
        Success output only gets sent to the stream after the test has stopped.
        """
        self.distReporter.startTest(self.test)
        self.assertEqual(self.stream.getvalue(), "")
        self.distReporter.addSuccess(self.test)
        self.assertEqual(self.stream.getvalue(), "")
        self.distReporter.stopTest(self.test)
        self.assertNotEqual(self.stream.getvalue(), "")

        Success output only gets sent to the stream after the test has stopped.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/_dist/test/test_distreporter.py