def test_serialize_list_with_items(self):
item_list = IdList()
item1 = Item('id1')
item2 = Item('id2')
item_list.add(item1)
item_list.add(item2)
assert item_list.serialize() == [item1.serialize(), item2.serialize()]
def test_serialize_empty_list(self):
item_list = IdList()
assert item_list.serialize() == []