def test_authenticDataDecode(self):
        """
        L{dns.Message.fromStr} decodes byte4 and assigns bit3 to
        L{dns.Message.authenticData}.
        """
        m = dns.Message()
        m.fromStr(MESSAGE_AUTHENTIC_DATA_BYTES)

        self.assertEqual(m.authenticData, 1)

        L{dns.Message.fromStr} decodes byte4 and assigns bit3 to
        L{dns.Message.authenticData}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_dns.py