Moq & RhinoMocks

使用Mock对象进行测试一般都会有以下三个关键步骤:

使用接口来描述需要测试的对象
为实际的产品代码实现这个接口
以测试为目的,在Mock对象中实现这个接口

在使用Mock对象的过程中，充分体现出了“面向接口编程”的设计原则，同时也促成类的良好设计。

自行实现Mock对象是相当繁琐的工作，让人幸运的是，在.NET世界中有多个优秀的Mock框架可以供大家选择，目前最常使用的无非Moq与Rhino Mocks这两个框架。两者的最新版本在Mocking API方面的用法已日趋一致，都依托Lambda表达式、泛型和扩展方法做了很大改进，目标都是让Mock对象以一种更自然的方式与多个单元测试框架进行集成，以一种清晰的语法来描述期望值、参数约束、返回值等，极大的方便开发者的使用。

由于Moq和Rhino Mocks都使用了Castle DynamicProxy这个类库动态生成代理类，因此对需要Mock的对象有一定的限制：所测试的方法必须是virtual类型。

下面就用一个例子来看看两者的不同实现(这个例子摘自Moq源代码包中的Samples，只是略做了些修改以便于展现两者的特点)：

需要进行测试的对象如下示之：

展开

折叠

public class OrdersPresenter
{
    private IRepository<Order> repository { get; set; }
    public IOrdersView View { get; set; }

    public OrdersPresenter(IOrdersView view, IRepository<Order> repository) {
        this.View = view;
        this.repository = repository;
        this.View.OrderSelected += (sender, args) => DoOrderSelection(args.Order);
    }

    public Order SelectedOrder { get; private set; }

    private void DoOrderSelection(Order selectedOrder) {
        // Do something when the view selects an order.
        SelectedOrder = selectedOrder;
    }

    public virtual void OnInit() {
        View.Orders = repository.FindAll();
    }           
}

下面是用这两个Mock框架分别实现的单元测试代码：

Moq 4.0

Rhino Mocks 3.6

[Test]
public void TestPresenterSelection() {
    // arrange
    var mView = new Mock<IOrdersView>();
    var mRepository = new Mock<IRepository<Order>>();
    var presenter = new OrdersPresenter(mView.Object, mRepository.Object);
    // check that the presenter has no selection by default
    Assert.Null(presenter.SelectedOrder);

    // raise event
    mView.Raise(io => io.OrderSelected += null, 
        new OrderEventArgs { Order = new Order("moq", 50) });

    // assert
    Assert.NotNull(presenter.SelectedOrder);
    Assert.AreEqual("moq", presenter.SelectedOrder.ProductName);
}

[Test]
public void TestPresenterSelection() {
    // arrange
    var mView = MockRepository.GenerateMock<IOrdersView>();
    var mRepository = MockRepository.GenerateMock<IRepository<Order>>();
    var presenter = new OrdersPresenter(mView, mRepository);
    // check that the presenter has no selection by default
    Assert.Null(presenter.SelectedOrder);

    // raise event
    mView.Raise(io => io.OrderSelected += null, null, 
        new OrderEventArgs { Order = new Order("moq", 50) });

    // assert
    Assert.NotNull(presenter.SelectedOrder);
    Assert.AreEqual("moq", presenter.SelectedOrder.ProductName);
}

[Test]
public void TestRetrieveOrders() {
    // arrange
    var mView = new Mock<IOrdersView>();
    var mRepository = new Mock<IRepository<Order>>();
    var presenter = new OrdersPresenter(mView.Object, mRepository.Object);

    List<Order> defaultOrders = new List<Order> 
        { new Order("moq"), new Order("RhinoMock") };

    mRepository.Setup(r => r.FindAll()).Returns(defaultOrders);

    // exercise mocks
    presenter.OnInit();
    // assert
    mView.VerifySet(v => v.Orders = defaultOrders);
}

[Test]
public void TestRetrieveOrders() {
    // arrange
    var mView = MockRepository.GenerateMock<IOrdersView>();
    var mRepository = MockRepository.GenerateStub<IRepository<Order>>();
    var presenter = new OrdersPresenter(mView, mRepository);

    List<Order> defaultOrders = new List<Order> 
        { new Order("moq"), new Order("RhinoMock") };

    mRepository.Stub(ir => ir.FindAll()).Return(defaultOrders);

    // exercise mocks
    presenter.OnInit();
    // assert
    mView.AssertWasCalled(v => v.Orders = defaultOrders);
}