def test_nonIntegerFound(self):
        """
        If the server responds with a non-integer where a message sequence
        number is expected, the L{Deferred} returned by L{IMAP4Client.search}
        fails with L{IllegalServerResponse}.
        """
        d = self._search()
        self._response([2, "foo", 10])
        self.failureResultOf(d, imap4.IllegalServerResponse)

        If the server responds with a non-integer where a message sequence
        number is expected, the L{Deferred} returned by L{IMAP4Client.search}
        fails with L{IllegalServerResponse}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/test/test_imap.py