我何时应该使用Moq的.As方法？

Question

我们什么时候需要使用.AsMoq提供的方法？

从快速入门文档:

// implementing multiple interfaces in mock
var foo = new Mock<IFoo>();
var disposableFoo = foo.As<IDisposable>();
// now the IFoo mock also implements IDisposable :)
disposableFoo.Setup(df => df.Dispose());

但我只是不明白我们为什么要那样做.你能给我一个实际的例子吗？

Answer 1

当您需要测试实现多个接口的对象时,可以使用As方法. 在此示例中,如果输入对象也实现了IDisposable,则测试代码具有特定行为.像这样的东西:

public void Execute(IFoo input)
{
    // do process...

    IDisposable disposable = input as IDisposable;
    if (disposable != null)
    {
        disposable.Dispose();
    }
}

类实现:

public class ConcreteFoo: IFoo, IDisposable
{
    ...
}

编辑:

Moq的配置需要:

var foo = new Mock<IFoo>(); 
var disposableFoo = foo.As<IDisposable>(); 
disposableFoo.Setup(df => df.Dispose());

// Verify whether the Dispose() method was called
// That's true only if we use the As method from Moq.
testedClass.Execute(disposableFoo);
disposableFoo.Verify(m => m.Dispose());

Answer 2

好的,这是一个例子.假设你有一个运输管理软件来管理汽车,飞行等的运动.有不同的车辆,但它们在陆地或空中移动(没有海来简化样本).

public interface IMovingOnLand
{
    string Move();
}

public interface IMovingInAir
{
    string Move();
}

并且有车辆/飞机的快速运输选项.

public interface IExpressTransport
{
    string MoveDirectly();
}

有一个运输经理班负责移动所有车辆/飞机.并且它处理快速传输方式与常规传输方式不同(为了简单起见,在此示例中,它仅根据是否为IExpressTransport打印不同的消息):

public class TransportManager
{
    public string MoveItem(IMovingInAir airCraft)
    {
        if (airCraft is IExpressTransport)
        {
            return "Message from an express aircraft: " +
                ((IExpressTransport)airCraft).MoveDirectly();
        }
        return "Message from an aircraft: " + airCraft.Move();
    }

    public string MoveItem(IMovingOnLand landVehicle)
    {
        if (landVehicle is IExpressTransport)
        {
            return "Message from an express land vehicle: " +
                landVehicle.Move() +
                ((IExpressTransport)landVehicle).MoveDirectly();
        }
        return "Message from a land vehicle: " + landVehicle.Move();
    }
}

现在,您想测试飞机的行为是否与汽车不同.而且,如果常规航班的处理方式与快速航班不同.因此,您将对象作为IMovingInAir对象进行测试IExpressTransport.要仅测试飞行行为,您只需将其创建为Mock<IMovingInAir>.但是要将航班延长至快速航班,您必须使用以下As<IExpressTransport>()方法:

[TestMethod]
public void TestTransportManager()
{
    TransportManager manager = new TransportManager();

    // Create a regular flight.
    var flight = new Mock<IMovingInAir>();
    flight.Setup(x => x.Move())
        .Returns("Air craft moved to next stop.");

    // Create a flight.
    var flightExpress = new Mock<IMovingInAir>();
    // Add standard behaviour.
    flightExpress
        .Setup(x => x.Move())
        .Returns("Air craft moved to next stop.");
    // Extend to express and add express flight behaviour.
    flightExpress
        .As<IExpressTransport>()
        .Setup(x => x.MoveDirectly())
        .Returns("Air craft moved directly to destination.");

    // Get the results.
    var res = manager.MoveItem(flight.Object);
    var resExp = manager.MoveItem(flightExpress.Object);

    // Sssert flight and express fligh returned different messages.
    Assert.AreNotEqual(res, resExp);

    // Assert the expected messages have been returned.
    Assert.AreEqual("Message from an aircraft: Air craft moved to next stop.", res);
    Assert.AreEqual("Message from an express aircraft: Air craft moved directly to destination.", resExp);
}