public void CanApplyCoffeeSpecialOfferToCoffeeTrolley_ShouldReturn32_00()
        {
            var checkout = new Checkout(_coffeeTrolley);

            var discountedTrolley = checkout.ApplyCoffeeSpecialOffer();
            var discountedTotal   = checkout.GetTotal();

            Assert.AreNotEqual(discountedTrolley, null);
            Assert.AreEqual(discountedTrolley.Count(), 4);
            Assert.AreEqual(discountedTotal, 32.00);
        }