@Override
    LlapTaskSchedulerService.DelayedTaskSchedulerCallable createDelayedTaskSchedulerCallable() {
      controlledTSCallable = new DelayedTaskSchedulerCallableControlled();
      return controlledTSCallable;
    }
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