def test_defaultPort(self):
        """
        When constructed using L{SecondaryAuthority.__init__}, the default port
        of 53 is used.
        """
        secondary = SecondaryAuthority('192.168.1.1', 'inside.com')
        self.assertEqual(secondary.primary, '192.168.1.1')
        self.assertEqual(secondary._port, 53)
        self.assertEqual(secondary.domain, 'inside.com')

        When constructed using L{SecondaryAuthority.__init__}, the default port
        of 53 is used.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_names.py