@Override
    protected void sendUpdateMessageAsync(TaskInfo ti, boolean newState) {
      synchronized (messageLock) {
        ++sentCount;
        messageLock.notifyAll();
      }
    }
Note: this only works for testing the lack of invocations from the main thread.
llap-tez/src/test/org/apache/hadoop/hive/llap/tezplugins/TestLlapTaskSchedulerService.java