@Override
  public boolean add(EpoxyModel<?> epoxyModel) {
    notifyInsertion(size(), 1);
    return super.add(epoxyModel);
  }
@Test
  public void testAdd() {
    modelList.add(new TestModel());
    modelList.add(new TestModel());

    verify(observer).onItemRangeInserted(3, 1);
    verify(observer).onItemRangeInserted(4, 1);
  }