@Test
public void testRetrieveVersionsListWhenNoVersions() throws IOException, FlowRetrievalException, NiFiRegistryException {

    final FlowUri flowUri = new FlowUri("http://localhost:18080", UUID.randomUUID().toString(), UUID.randomUUID().toString());
    when(flowSnapshotClient.getSnapshotMetadata(flowUri.getBucketId(), flowUri.getFlowId())).thenReturn(Collections.emptyList());
    final List<VersionedFlowSnapshotMetadata> returnedVersions = flowRetrievalService.getVersions(flowUri);
    assertNotNull(returnedVersions);
    assertEquals(0, returnedVersions.size());
}