void handleJobPriorityChange(AllocateResponse response) {
    Priority applicationPriority = response.getApplicationPriority();
    if (null != applicationPriority) {
      Priority priorityFromResponse = Priority
          .newInstance(applicationPriority.getPriority());
      // Update the job priority to Job directly.
      getJob().setJobPriority(priorityFromResponse);
    }
  }
@Test
  public void testIfApplicationPriorityIsNotSet() {
    Job mockJob = mock(Job.class);
    RMCommunicator communicator = mock(RMCommunicator.class);
    ClientService service = mock(ClientService.class);
    AppContext context = mock(AppContext.class);
    AMPreemptionPolicy policy = mock(AMPreemptionPolicy.class);
    when(communicator.getJob()).thenReturn(mockJob);
    RMContainerAllocator allocator = new RMContainerAllocator(service, context,
        policy);
    AllocateResponse response = Records.newRecord(AllocateResponse.class);
    allocator.handleJobPriorityChange(response);
  }