def test_parametrizedClock(self):
        """
        The clock used by L{ReconnectingClientFactory} can be parametrized, so
        that one can cleanly test reconnections.
        """
        clock = Clock()
        factory = ReconnectingClientFactory()
        factory.clock = clock

        factory.clientConnectionLost(FakeConnector(), None)
        self.assertEqual(len(clock.calls), 1)

        The clock used by L{ReconnectingClientFactory} can be parametrized, so
        that one can cleanly test reconnections.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_factories.py