@Test
public void testAppsRace() throws Exception {

  // mock up an RM that returns app reports for apps that don't exist
  // in the RMApps list
  ApplicationId appId = ApplicationId.newInstance(1, 1);
  ApplicationReport mockReport = mock(ApplicationReport.class);
  when(mockReport.getApplicationId()).thenReturn(appId);
  GetApplicationsResponse mockAppsResponse =
      mock(GetApplicationsResponse.class);
  when(mockAppsResponse.getApplicationList())
    .thenReturn(Arrays.asList(new ApplicationReport[] { mockReport }));
  ClientRMService mockClientSvc = mock(ClientRMService.class);
  when(mockClientSvc.getApplications(isA(GetApplicationsRequest.class)))
      .thenReturn(mockAppsResponse);
  ResourceManager mockRM = mock(ResourceManager.class);
  RMContextImpl rmContext = new RMContextImpl(null, null, null, null, null,
      null, null, null, null, null);
  when(mockRM.getRMContext()).thenReturn(rmContext);
  when(mockRM.getClientRMService()).thenReturn(mockClientSvc);
  rmContext.setNodeLabelManager(mock(RMNodeLabelsManager.class));
  RMWebServices webSvc = new RMWebServices(mockRM, new Configuration(),
      mock(HttpServletResponse.class));
  final Set<String> emptySet =
      Collections.unmodifiableSet(Collections.<String>emptySet());
  // verify we don't get any apps when querying
  HttpServletRequest mockHsr = mock(HttpServletRequest.class);
  AppsInfo appsInfo = webSvc.getApps(mockHsr, null, emptySet, null,
      null, null, null, null, null, null, null, emptySet, emptySet, null,
      null);
  assertTrue(appsInfo.getApps().isEmpty());
  // verify we don't get an NPE when specifying a final status query
  appsInfo = webSvc.getApps(mockHsr, null, emptySet, "FAILED",
      null, null, null, null, null, null, null, emptySet, emptySet, null,
      null);
  assertTrue(appsInfo.getApps().isEmpty());
}