Delta<VisualItem> delta = Delta.createAddedDelta(addedElements);
// XXX right now underTest does not care what the event is, but it may
// in the future, feel free to implement the event in this test in the
// future
handler.onVisualItemContainerChanged(new VisualItemContainerChangeEvent(
visualItemContainer, delta));
// verify that we set the viewModel
verify(visualizationModel, times(1)).setResolver(slots[0], resolver1);
}