Question

Here is my problem:

I have an n-tiers application for which I have to write unit tests. Unit tests are for the business layer.

I have a method to test called Insert() and this one use two protected methods from inheritance and call directly a method from Data access layer.

So I have made a mock object for the DAL. But here is the point, in a (edit 🙂 protected method from inheritance, It will use another object from DAL! It seems it is not possible to mock this one!

Here is the method for test code:

public int Insert(MYOBJECT aMyObject)
    {
            //first inherited method use the FIRSTDALOBJECT so the mock object --> No problem
            aMyObject.SomeField= FirstInherited();

            //Second inherited method (see after) --> my problem
            aMyObject.SomeOtherField = SecondInherited();

            // Direct access to DALMethod, use FIRSTDALOBJECT so the mock -->No Problem
            return this.FIRSTDALOBJECT.Insert(aMyObject);             
     }

Here is the SecondInherited method:

 protected string SecondInherited ()
    { 
        // Here is my problem, the mock here seems not be possible for seconddalobject                                          
        return ( new SECONDDALOBJECT Sdo().Stuff());
    }

And here is the unit test method code :

    [TestMethod()]
    public void InsertTest()
    {
        BLLCLASS_Accessor target = new BLLCLASS_Accessor();
        MYOBJECT aMyObject = new MYOBJECT { SomeField = null, SomeOtherField = 1 };
        int expected = 1;
        int actual;

        //mock
        var Mock = new Mock<DAL.INTERFACES.IFIRSTDALOBJECT>();
        //Rec for calls
        List<SOMECLASS> retour = new List<SOMECLASS>();
        retour.Add(new SOMECLASS());

        //Here is the second call (last from method to test)
        Mock
            .Setup(p => p.Insert(aMyObject))
            .Returns(1);

        // Here is the first call (from the FirstInherited())
        Mock
            .Setup(p => p.GetLast())
            .Returns(50);
        // Replace the real by the mock
        target.demande_provider = Mock.Object;

        actual = target.Insert(aMyObject);
        Assert.AreEqual(/*Some assertion stuff*/);
    }

Thank you for reading all the question 🙂 Hope it is clear enough.

Answer 1

Your text seems to say that SecondInherited is private, while in the code example it is protected. Anyway, if it is not protected, I would suggest changing its access qualifier as the first step.

You can create a subclass solely for testing purposes, and override SecondInherited there to avoid creating SECONDDALOBJECT and just return some value suitable for your tests.

This way you can write your first unit test(s) with minimal changes to the class being tested, thus minimizing the chances of breaking something. Once you have the unit tests in place, these allow you to do more refactoring safely, eventually achieving a better (more testable / mockable) design, such as using Dependency Injection, or a Factory. (I would probably prefer an Abstract Factory over Factory Method here, as the latter would practically force you to keep subclassing the tested class).

The fundamental, highly recommended book for learning this technique (and many more) is Working Effectively With Legacy Code.