@Override
  public boolean addAll(Collection<? extends EpoxyModel<?>> c) {
    notifyInsertion(size(), c.size());
    return super.addAll(c);
  }
@Test
  public void testAddAll() {
    List<EpoxyModel<?>> newModels = new ArrayList<>();
    newModels.add(new TestModel());
    newModels.add(new TestModel());

    modelList.addAll(newModels);
    verify(observer).onItemRangeInserted(3, 2);
  }