def test_errorsIsolated(self):
        """
        Check that an error logged in one test doesn't fail the next test.
        """
        t1 = self.MockTest('test_single')
        t2 = self.MockTest('test_silent')
        t1(self.result)
        t2(self.result)
        self.assertEqual(len(self.result.errors), 1)
        self.assertEqual(self.result.errors[0][0], t1)
        self.assertEqual(1, self.result.successes)

        Check that an error logged in one test doesn't fail the next test.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/test/test_log.py