public void StackSystemTest() { var em = new EntityManager(); var entity = em.CreateEntity(); var inventory = new Inventory(); entity.AddComponent(inventory); var itemEntity = em.CreateEntity(); var itemComponent = new Item() { Type = "widget" }; itemEntity.AddComponent <Stackable>(); itemEntity.AddComponent(itemComponent); inventory.Items.Add(itemEntity); itemEntity = em.CreateEntity(); itemEntity.AddComponent(itemComponent); itemEntity.AddComponent <Stackable>(); inventory.Items.Add(itemEntity); var stackSystem = new StackSystem(_mockEngine); var stacks = stackSystem.GetStacks(entity); Assert.AreEqual(2, stacks["widget"]); }