def _make_fake_message(self, user_id, page_id, payload):
        """
        Creates a fake message for the given user_id. It contains a postback
        with the given payload.
        """

        event = {
            'sender': {
                'id': user_id,
            },
            'recipient': {
                'id': page_id,
            },
            'postback': {
                'payload': ujson.dumps(payload),
            },
        }

        return FacebookMessage(event, self, False)
Creates a fake message for the given user_id. It contains a postback
        with the given payload.