def test_postOptionsNoSubCommand(self):
        """
        L{TwistOptions.postOptions} raises L{UsageError} is it has no
        sub-command.
        """
        self.patchInstallReactor()

        options = TwistOptions()

        self.assertRaises(UsageError, options.postOptions)

        L{TwistOptions.postOptions} raises L{UsageError} is it has no
        sub-command.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/twist/test/test_options.py