def test_mx(self):
        """
        The repr of a L{dns.Record_MX} instance includes the preference, name,
        and TTL fields of the record.
        """
        self.assertEqual(
            repr(dns.Record_MX(13, b'mx.example.com', 2)),
            "<MX preference=13 name=mx.example.com ttl=2>")

        The repr of a L{dns.Record_MX} instance includes the preference, name,
        and TTL fields of the record.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_dns.py