@Override
  public boolean add(EpoxyModel<?> epoxyModel) {
    notifyInsertion(size(), 1);
    return super.add(epoxyModel);
  }
@Test
  public void testAddAtIndex() {
    modelList.add(0, new TestModel());
    modelList.add(2, new TestModel());

    verify(observer).onItemRangeInserted(0, 1);
    verify(observer).onItemRangeInserted(2, 1);
  }