@Test
public void shouldReturnNullWhenObjectListingIsSize0() {

    ObjectListing listing = new ObjectListing();
    doReturn(listing).when(mockClient).listObjects(any(ListObjectsRequest.class));
    S3ArtifactStore store = new S3ArtifactStore(mockClient, "foo-bar");
    String prefix = store.getLatestPrefix("pipeline", "stage", "job", "1");
    assertNull(prefix);
}