def test_invalid_in_reply_to(self):
        msg = {
            'content': 'foo',
            'in_reply_to': '1',  # this doesn't exist
        }

        url = '%s/%s/messages.json' % (self.url, self.conversation.key)
        response = yield http_request_full(url, json.dumps(msg),
                                           self.auth_headers, method='PUT')
        self.assert_bad_request(response, 'Invalid in_reply_to value')