Moq中的抽象工厂单元测试

Question

Suppose I have following class called SomeClass as defined:

public SomeClass
{
    private IThingFactory _thingFactory;

    public SomeClass(IThingFactory thingFactory)
    {
        _thingFactory = thingFactory;
    }

    public IThing CreateThing(int a, int b, string c)
    {
        IThing thing = _thingFactory.MakeEmptyThing();
        thing.MakeFromFields(a, b, c);

        return thing;
    }
}

The spec of the CreateThing(int a, int b, string c) method is that it takes an int a , int b , string c and returns an IThing with the corresponding properties. (so internally maybe new Thing(a, b, c) )

However the implementation delegates that work to a IThingFactory and Thing populates itself.

So now I'm trying to unit test the method CreateThing() , but I'm not exactly sure how it should work.

Here's what I tried:

Based off of the principles of mocking dependencies, I created a Mock<IThingFactory> and gave it to the constructor of SomeClass

_mockThingFactory = new Mock<IThingFactory>();
someClass = new SomeClass(_mockThingFactory.Object);

Afterwards, I called the method under test

IThing thing = _someClass.CreateThing(It.IsAny<int>(), 
    It.IsAny<int>(), 
    It.IsAny<string>>());

And to assert, I'm not sure. Should I verify that MakeEmptyThing() was called? What do I do with thing.MakeFromFields(a, b, c); ?

Answer 1

You should look at results of the method under test. In this case result is "factory constructed object and particular method of the object is called with arguments".

To test that you can return mock object from CreateThing and than check if MakeFromFields on it called with expected parameters (ie Using Moq, How to setup a method call with an input parameter as an object with expected property values? ).

var mockThing = new Mock<IThing>();
_mockThingFactory.Setup(f=> f.MakeEmptyThing()).Returns(mockThing.Object);

classUnderTest =  new SomeClass(_mockThingFactory.Object);  
classUnderTest.CreateThing(1,2,3);
mockThing.Verify(....)

Note that it may be better to move MakeFromFields to factory. Also consider using existing DI framework (like Unity) to deal with all object creation.