def test_UIDGID(self):
        """
        Check UID/GID switches when current effective UID/GID is non-root.
        """
        self._testUIDGIDSwitch(1, 1, 0, 0, [0, 1], [0, 1])
        self._testUIDGIDSwitch(1, 1, 0, 1, [0, 1], [])
        self._testUIDGIDSwitch(1, 1, 1, 0, [0, 1, 0, 1], [0, 1])
        self._testUIDGIDSwitch(1, 1, 1, 1, [], [])
        self._testUIDGIDSwitch(1, 1, 2, 1, [0, 2, 0, 1], [])
        self._testUIDGIDSwitch(1, 1, 1, 2, [0, 1, 0, 1], [2, 1])
        self._testUIDGIDSwitch(1, 1, 2, 2, [0, 2, 0, 1], [2, 1])

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