public void should_get_count_of_item_type() { // include this item, correct type var item1 = new ItemBuilder() .With(i => i.ItemSource, new ItemSourceBuilder() .With(i => i.Id, 5) .BuildAndSave()) .BuildAndSave(); // exclude this item, different type var item2 = new ItemBuilder() .With(i => i.ItemSource, new ItemSourceBuilder() .With(i => i.Id, 7) .BuildAndSave()) .BuildAndSave(); var player = new PlayerBuilder() .With(i => i.Items, new List <Item>()) .BuildAndSave(); player.GiveItem(item1); Assert.That(player.GetCountOfItem(5), Is.EqualTo(1)); }