def test_currentUID(self):
        """
        If the current uid is the same as the uid passed to L{util.switchUID},
        then initgroups does not get called, but a warning is issued.
        """
        uid = self.mockos.getuid()
        util.switchUID(uid, None)
        self.assertEqual(self.initgroupsCalls, [])
        self.assertEqual(self.mockos.actions, [])
        currentWarnings = self.flushWarnings([util.switchUID])
        self.assertEqual(len(currentWarnings), 1)
        self.assertIn('tried to drop privileges and setuid %i' % uid,
                      currentWarnings[0]['message'])
        self.assertIn(
            'but uid is already %i' % uid, currentWarnings[0]['message'])

        If the current uid is the same as the uid passed to L{util.switchUID},
        then initgroups does not get called, but a warning is issued.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_util.py