How do I moq a ISingleResult? Should I? or there is a better method?

Question

I have an action method like this in my controller

public ActionResult Index()
{
    using (NorthwindDataContext db = new NorthwindDatacontext())
    {
        var results = db.GetRecordSets(arg1, ....).ToList();
        // use results as list
    }

    return View();
}

and I wanted to start making tests for it (yes, after it was built, not before... but the code was written before I started to use TDD so... )

and I figured out that adding a property such as this one to the controller

public delegate NorthwindDatacontext ContextBuilderDelegate();

public ContextBuilderDelegate ContextBuilder { get; set; }

I could add in the constructor something like this...

ContextBuilder = () => new NorthwindDatacontext();

then I could test the ActionMethod setting the ContextBuilder property with a mock of NorthwindDatacontext

var controller              = new MyController();
var mockDataContext         = new Mock<NorthwindDatacontext>();
controller.ContextBuilder   = () => mockDataContext.Object;

But... I found no way to use this because all methods of NorthwindDatacontext use ISingleResult as returnType and I cant find the way to create an object with that interface. I've tried this

var theResult                  = new List<GetRecordSetsResult>();
// fill the data structure here with the provided result...

mockDataContext.Setup(c => c. GetRecordSets()).Returns(theResult as
                                            ISingleResult<GetRecordSetsResult>);

but it doesn't work because theResult is null when converted to ISingleResult.

Is there any way to create a ISingleResult object to test this way or I'm doing the incorrect way to do things here?

Thanks in Advance

Answer 1

ToList() is an extension method for IEnumerable, which is easy to mock, because it only has one member method -- GetEnumerator().

Still you might have problems mocking NorthwindDataContext class, if its methods are not virtual...

Anyways, that's how I solved a similar problem in my sandbox, hope it helps:

public class MyType
{
    public virtual ISingleResult<int> ReturnSomeResult() { throw new NotImplementedException(); }
}

[TestMethod]
public void TestMethod1()
{
    var mockMyType = new Mock<MyType>();
    var mockSingleResult = new Mock<ISingleResult<int>>();
    IEnumerable<int> someEnumerable = new int[] {1,2,3,4,5};
    mockSingleResult.Setup(result => result.GetEnumerator()).Returns(someEnumerable.GetEnumerator());
    mockMyType.Setup(myType => myType.ReturnSomeResult()).Returns(mockSingleResult.Object);

    Assert.AreEqual(15, mockMyType.Object.ReturnSomeResult().ToList().Sum());
}

Answer 2

I created a class that implemented ISingleResult and just put a List in it. I am fairly new to this type of coding, so while this worked for me, use at your own risk (and if you see holes post a comment).

class SingleResult<T>:ISingleResult<T>
{
    readonly List<T> _list = new List<T>();

    public void Add(T item)
    {
        _list.Add(item);
    }

    #region Interface Items

    public IEnumerator<T> GetEnumerator()
    {
        return _list.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    public object ReturnValue { get { return _list; } }

    public void Dispose() { }

    #endregion
}

This can then be used to return in part of a mock. This is how I ended up using it with Rhino Mocks:

[TestMethod]
public void TestSomething()
{
    //Arrange
    // Make a data context and DAL
    var _ctx = MockRepository.GenerateMock<IDataClassesDataContext>();
    var someDALClass = new SomeDALClass(_ctx);

    User testUser = UserObjectHelper.TestUser();
    SingleResult<User> userList = new SingleResult<User> { testUser };

    // Indicate that we expect a call the to sproc GetUserByUserID
    _ctx.Expect(x => x.GetUserByUserID(testUser.UserID)).Return(userList);

    //Act
    someDALClass.UpdateUser(testUser);

    //Assert
    Assert.IsTrue(SomeTestCondition());
}