@Override
        public int compareTo(TaskDescriptor o) {
            if (timestamp < o.timestamp) return -1;
            if (timestamp > o.timestamp) return 1;
            if (sequenceId < o.sequenceId) return -1;
            if (sequenceId > o.sequenceId) return 1;
            return 0;
        }
Invoke registered MessageHandler with message
@param message message to "send"
documentapi/src/test/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSessionTestCase.java