def test_fetchWithPartialValidArgument(self):
        """
        If by any chance, extra bytes got appended at the end of a valid
        FETCH arguments, the client should get a BAD - arguments invalid
        response.

        See U{RFC 3501<http://tools.ietf.org/html/rfc3501#section-6.4.5>},
        section 6.4.5,
        """
        # We need to clear out the welcome message.
        self.transport.clear()
        # Let's send out the faulty command.
        self.server.dataReceived(b"0001 FETCH 1 FULLL\r\n")
        expected = b"0001 BAD Illegal syntax: Invalid Argument\r\n"
        self.assertEqual(self.transport.value(), expected)
        self.transport.clear()
        self.server.connectionLost(error.ConnectionDone("Connection closed"))

        If by any chance, extra bytes got appended at the end of a valid
        FETCH arguments, the client should get a BAD - arguments invalid
        response.

        See U{RFC 3501<http://tools.ietf.org/html/rfc3501#section-6.4.5>},
        section 6.4.5,
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py