verify(mockRMClient, times(2)).
addContainerRequest(requestCaptor.capture());
CookieContainerRequest request1 = requestCaptor.getValue();
scheduler.allocateTask(mockTask2, mockCapability, hosts,
racks, mockPriority, null, mockCookie2);
drainableAppCallback.drain();
verify(mockRMClient, times(3)).
addContainerRequest(requestCaptor.capture());
CookieContainerRequest request2 = requestCaptor.getValue();
scheduler.allocateTask(mockTask3, mockCapability, hosts,
racks, mockPriority, null, mockCookie3);