OpenDoor4.cs

// tests with mocked dependencies

[TestClass]
public class CheckoutTests
{
    private Mock<IPriceList> drinksMenu;
    private Mock<IClock> clock;
    private List<Order> orders;

    [TestInitialize]
    public void Setup()
    {
        // create mock price list
        this.drinksMenu = new Mock<IPriceList>();

        // setup lookup method for three drinks
        drinksMenu.Setup(dm => dm.LookupPrice("Little Creatures Pale Ale")).Returns(7);
        drinksMenu.Setup(dm => dm.LookupPrice("Pigs Fly Pale Ale")).Returns(8);
        drinksMenu.Setup(dm => dm.LookupPrice("Hitachino White Ale")).Returns(9);

        // create mock clock
        this.clock = new Mock<IClock>();

        // create the list of orders
        this.orders = new List<Order>();

        orders.Add(new Order() { Drink = "Little Creatures Pale Ale", Quantity = 2 });
        orders.Add(new Order() { Drink = "Pigs Fly Pale Ale", Quantity = 1 });
        orders.Add(new Order() { Drink = "Hitachino White Ale", Quantity = 1 });
    }

    [TestMethod]
    public void CalculateCostNormalTest()
    {
        // setup clock to be 6:26pm on Sunday 30th of the June 2013
        this.clock.Setup(c => c.GetDateTimeNow()).Returns(new DateTime(2013, 06, 30, 18, 26, 00));

        var checkout = new Checkout(this.drinksMenu.Object, this.clock.Object);

        Assert.AreEqual(34.10m, checkout.CalculateCost(this.orders));
    }

    [TestMethod]
    public void CalculateCostHappyHourTest()
    {
        // setup clock to be 5:13pm on Friday 28th of the June 2013
        this.clock.Setup(c => c.GetDateTimeNow()).Returns(new DateTime(2013, 06, 28, 17, 13, 00));

        var checkout = new Checkout(this.drinksMenu.Object, this.clock.Object);

        Assert.AreEqual(17.05m, checkout.CalculateCost(this.orders));
    }
}