ContainerId registerContainer(int containerIdx, int hostIdx) {
      ContainerId containerId = ContainerId.newInstance(appAttemptId, containerIdx);
      taskCommunicator.registerRunningContainer(containerId, HOSTS[hostIdx], RPC_PORT);
      return containerId;
    }
Wrapper class which is responsible for setting up various mocks required for different tests.
llap-tez/src/test/org/apache/hadoop/hive/llap/tezplugins/TestLlapTaskCommunicator.java