def test_sendUnhandledError(self):
        """
        L{CommandDispatcher} should relay its unhandled errors in responding to
        boxes to its boxSender.
        """
        err = RuntimeError("something went wrong, oh no")
        self.sender.expectError()
        self.dispatcher.unhandledError(Failure(err))
        self.assertEqual(len(self.sender.unhandledErrors), 1)
        self.assertEqual(self.sender.unhandledErrors[0].value, err)

        L{CommandDispatcher} should relay its unhandled errors in responding to
        boxes to its boxSender.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_amp.py