def testAdvance(self):
        """
        Test that advancing the clock will fire some calls.
        """
        events = []
        c = task.Clock()
        call = c.callLater(2, lambda: events.append(None))
        c.advance(1)
        self.assertEqual(events, [])
        c.advance(1)
        self.assertEqual(events, [None])
        self.assertFalse(call.active())

        Test that advancing the clock will fire some calls.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_task.py