def test_root(self):
        """
        Check UID/GID switches when current effective UID is root.
        """
        self._testUIDGIDSwitch(0, 0, 0, 0, [], [])
        self._testUIDGIDSwitch(0, 0, 1, 0, [1, 0], [])
        self._testUIDGIDSwitch(0, 0, 0, 1, [], [1, 0])
        self._testUIDGIDSwitch(0, 0, 1, 1, [1, 0], [1, 0])

        Check UID/GID switches when current effective UID is root.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_util.py