@Test
public void testGetFlowSnapshotsWhenNoSnapshots() {

    final BucketEntity existingBucket = new BucketEntity();
    existingBucket.setId("b1");
    existingBucket.setName("My Bucket");
    existingBucket.setDescription("This is my bucket");
    existingBucket.setCreated(new Date());
    when(metadataService.getBucketById(existingBucket.getId())).thenReturn(existingBucket);
    // return a flow with the existing snapshot when getFlowById is called
    final FlowEntity existingFlow = new FlowEntity();
    existingFlow.setId("flow1");
    existingFlow.setName("My Flow");
    existingFlow.setDescription("This is my flow.");
    existingFlow.setCreated(new Date());
    existingFlow.setModified(new Date());
    existingFlow.setBucketId(existingBucket.getId());
    final Set<FlowSnapshotEntity> snapshots = new HashSet<>();
    when(metadataService.getFlowById(existingFlow.getId())).thenReturn(existingFlow);
    final SortedSet<VersionedFlowSnapshotMetadata> retrievedSnapshots = registryService.getFlowSnapshots(existingBucket.getId(), existingFlow.getId());
    assertNotNull(retrievedSnapshots);
    assertEquals(0, retrievedSnapshots.size());
}