def METHOD_NAME(small_robot_mp4_vid):
    groupset = FrameGroupSet(method="testing")
    items = [FrameItem(small_robot_mp4_vid, i) for i in range(10)]
    more_items = [FrameItem(small_robot_mp4_vid, i) for i in range(13, 16)]
    for item in items:
        groupset.append_to_group(group=item.frame_idx % 3, item=item)
    assert groupset.get_item_group(items[0]) == 0
    assert groupset.get_item_group(items[1]) == 1
    assert groupset.get_item_group(items[2]) == 2
    assert groupset.get_item_group(items[3]) == 0
    assert set(groupset.all_items) == set(items)
    groupset.extend_group_items(group=3, item_list=more_items)
    assert groupset.get_item_group(more_items[0]) == 3
    assert set(groupset.all_items) == set(items).union(more_items)
    sampled_groupset = groupset.sample(per_group=2)
    for group, item_list in sampled_groupset.groups:
        assert len(item_list) == 2