在MVC中使用Mock进行单元测试

Question

I am trying to implement an unit test for a method in my class. How could I mock a base class indexer on the class method I am testing? Below code snippet should give a clear picture of my requirement.

public class MyClass:MyBase
{
  public string returnString(string str1)
  {
     var xyz=base[str1];
     //My code to unit test is here
  }
}

public class MyBase
{
  public virtual string this[string str1]
  {
     return "prefix"+str1;
  }
}

I would like to stub my base class indexer with a dummy string and test my actual code. How can I do that? Thanks for any help on this in advance.

Sree.

Answer 1

Normally not recommended practice, but in this case "appropriate": mock your class under test. Of course in this case, you'd only mock out stuff that's specific to the base class and not overridden in any way your descendant under test. This ensures that the base class' behavior is mocked and therefore under control of the tests when testing the descendant's methods.

In your example, you would create a mock of MyClass but only mock out the inherited (MyBase's) constructor, thus making sure that all other methods run "as coded", and then assert against the mocked instance.

Answer 2

I don't see the reason to stub your base class, since you can mock your class under test. I'll show you.

I added return statement to returnString() method, just for assertion to complete the test:

public string returnString (string str1)
{
    var xyz = base [str1];
    return xyz;
}

And now the test:

[TestMethod, Isolated]
public void TestIndexerFake()
{
    //Arrange
    var MyClassFake = Isolate.Fake.AllInstances<MyClass>(Members.CallOriginal);
    Isolate.WhenCalled(() => MyClassFake["test"]).WillReturn("fake!");

    //Act
    MyClass target = new MyClass();
    var result = target.returnString("test");

    //Assert
    Assert.AreEqual("fake!", result);
}

I'm using Typemock Isolator and MsTest.

Hope it helps!