Moq与Unity Container单元测试

Question

below is an example of production code that I am trying to unit test. I am struggling to resolve a dependency to a concrete class that is being used.

public MyClass(IUnityContainer container)
{
    this.unityContainer = container;
}

public string DoWork()
{
     var sender = unityContainer.Resolve<IInterface>();  // how to setup this object
     var json = sender.Send("something");
     var value = serializer.Deserialize<SomeModel>(json);
     return value.url;
}

I want to mock out the IInterface used by this method. How do I set that up in my unit test code? I feel like there is something missing here. this has a smell of an anti-pattern.....

Answer 1

this has a smell of an anti-pattern

It certainly does. Why are you passing an instance to your DI container into your business object's constructor? You should pass the IInterface instead. See Dependency Injection container in constructor .

Anyway to make this work in your unit test, you just have to set up the container to return an instance or a mock of IInterface . Like this:

public void MyUnitTest()
{
    IUnityContainer myContainer = new UnityContainer();
    myContainer.RegisterType<IInterface, YourInstance>();

    MyClass classUnderTest = new MyClass(myContainer);
    classUnderTest.DoWork();

    Assert...
}

See How to use Unity.RegisterType with Moq? to mock the YourInstance .

Answer 2

I agree with CodeCaster. The typical pattern would be to accept a parameter of type IInterface in the constructor and assign it to a class-level variable.

public MyClass(IInterface sender)
{
    this.sender = sender;
}

When testing, simply pass in your moq. That said, there are times when I dislike passing in a dependency through the constructor. Such as:

• I may need multiple instances of a class
• The object is only needed conditionally.
• The class's constructor may depend on additional values that are not determined until run time.

In those cases, passing the container as a parameter is the only solution I've come across. Just be sure to register your initial instance of the container with itself. Otherwise, the DI will provide your constructor with a new (empty) container. If anyone has a better pattern, particularly one that works with Unity, I'd love to see it.