public void When_promotion_applies() { var productCatalog = new ProductCatalog(); productCatalog.AddQuantityDiscount("apple", 3, 2); productCatalog.AddProduct("apple", 0.75m); var sut = new QuantityDiscountRule(productCatalog); var promotions = new Promotions(new List<IPromotionalDiscountRule>() { sut }); var lineItem = new LineItem("apple", 7, productCatalog, promotions); var actual = sut.PromotionApplies(lineItem); Assert.That(actual, Is.True); }