def test_HighestOnlyProgresses(self):
        """
        Test that downloading a message with a smaller index than the current
        LAST response doesn't change the LAST response.
        """
        p = self.pop3Server
        s = self.pop3Transport
        p.mbox.messages.append(self.extraMessage)

        p.lineReceived(b'RETR 2')
        self._flush()
        p.lineReceived(b'TOP 1 10')
        self._flush()
        s.seek(0)
        s.truncate(0)
        p.lineReceived(b'LAST')
        self.assertEqual(
            s.getvalue(),
            b'+OK 2\r\n')

        Test that downloading a message with a smaller index than the current
        LAST response doesn't change the LAST response.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_pop3.py