public void Given_TwoButterOneBread_WhenBuyTwoButterGetOneBreadHalfPrice_ReturnHalf() { var testData = new List <Product> { new Product { PriceInPounds = 1.00m, DisplayName = "Bread", Quantity = 1, Id = Product.BreadId }, new Product { PriceInPounds = 0.80m, DisplayName = "Butter", Quantity = 2, Id = Product.ButterId } }; var result = _offerService.BuyTwoButterGetOneBreadHalfPrice(testData); Assert.AreEqual(0.50m, result); }