@Test
  public void testStartWorkWithLastActiveJobModelWithNullActiveJobModelVersion() {
    final JobCoordinatorListener mockListener = mock(JobCoordinatorListener.class);
    ZkJobCoordinator zkJobCoordinator = new ZkJobCoordinator(PROCESSOR_ID, new MapConfig(),
        new NoOpMetricsRegistry(), zkUtils, zkMetadataStore, coordinatorStreamStore);

    zkJobCoordinator.setListener(mockListener);

    zkJobCoordinator.startWorkWithLastActiveJobModel();

    verifyZeroInteractions(mockListener);
    assertNull("Expected active job model to be null", zkJobCoordinator.getActiveJobModel());
  }
Test job model version changed without any changes to work assignment. In this scenario, existing work should
not be stopped a.k.a processor shouldn't stop the container. However, the processor proceeds to join the barrier
to notify its acceptance on the proposed job model.
samza-core/src/test/java/org/apache/samza/zk/TestZkJobCoordinator.java