def test_usernames(self):
        """
        CompleteUsernames produces zsh shell-code that completes system
        usernames.
        """
        c = usage.CompleteUsernames()
        out = c._shellCode('some-option', usage._ZSH)
        self.assertEqual(out, ':some-option:_users')

        c = usage.CompleteUsernames(descr='some action', repeat=True)
        out = c._shellCode('some-option', usage._ZSH)
        self.assertEqual(out, '*:some action:_users')

        CompleteUsernames produces zsh shell-code that completes system
        usernames.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_usage.py