测试工厂模式

Question

I have the small sample factory pattern implementation below, and was wondering if someone can help me write proper Moq unit test cases, for maximum code coverage:

public class TestClass
{ 
    private readonly IService service;

    public TestClass(Iservice service)
    {
        this.service = service;
    }

    public void Method(string test)
    {
        service = TestMethod(test);
        service.somemethod();
    }

    private IService TestMethod(string test)
    {
        if(test == 'A')
            service = new A();
        if(test == 'B')
            service = new B();
        return service;
    }
}

I am looking for some help in Testing the TestClass and more importantly TestMethod when i send Mock, for example my test method goes below :

[TestMethod]
public void TestCaseA()
{
    Mock<IService> serviceMock = new Mock<Iservice>(MockBehaviour.strict);
    TestClass tClass = new TestClass(serviceMock.Object);

    // The Question is, what is best approach to test this scenario ?
    // If i go with below approach, new A() will override serviceMock
    // which i am passing through constructor.
    var target = tClass.Method("A");
}

Answer 1

You would not mock the TestClass , because that is what you are testing.

For this to work, you need to make a read-only property for service .

public IService Service { get; private set; }

You need to test the way that both the constructor and Method modify the state(in this case Service ) of the TestClass instance.

Your test would look something like the following for testing the Method for the B test case:

[TestMethod]
public void TestSomeMethod()
{
    // Arrange/Act
    var target = new TestClass((new Mock<IService>()).Object);
    target.Method("B");

    // Assert
    Assert.IsInstanceOfType(target.Service, typeof(B));
}

Your test would look something like the following for testing the constructor for the A test case:

[TestMethod()]
public void TestCasesA()
{
    // Arrange/Act
    var target = new TestClass("A");

    // Assert
    Assert.IsInstanceOfType(target.service, typeof(A));
}

I would recommend only using the constructor approach to inject your IService . This allows you to have an immutable object that will reduce the state of your application.