def test_identityOfListOpenFDsChanges(self):
        """
        Check that the identity of _listOpenFDs changes after running
        _listOpenFDs the first time, but not after the second time it's run.

        In other words, check that the monkey patching actually works.
        """
        # Create a new instance
        detector = process._FDDetector()

        first = detector._listOpenFDs.__name__
        detector._listOpenFDs()
        second = detector._listOpenFDs.__name__
        detector._listOpenFDs()
        third = detector._listOpenFDs.__name__

        self.assertNotEqual(first, second)
        self.assertEqual(second, third)

        Check that the identity of _listOpenFDs changes after running
        _listOpenFDs the first time, but not after the second time it's run.

        In other words, check that the monkey patching actually works.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_posixprocess.py