def test_secondary(self):
        """
        An argument of the form C{"ip/domain"} is parsed by L{Options} for the
        I{--secondary} option and added to its list of secondaries, using the
        default DNS port number.
        """
        options = Options()
        options.parseOptions(['--secondary', '1.2.3.4/example.com'])
        self.assertEqual(
            [(('1.2.3.4', PORT), ['example.com'])], options.secondaries)

        An argument of the form C{"ip/domain"} is parsed by L{Options} for the
        I{--secondary} option and added to its list of secondaries, using the
        default DNS port number.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_tap.py