Question

In the .net 3.5 project that I am working on right now, I was writing some tests for a service class.

public class ServiceClass : IServiceClass
{
     private readonly IRepository _repository;

     public ServiceClass(IRepository repository)
     {
          _repository = repository;
     }

     #region IServiceClass Members

     public IEnumerable<ActionType> GetAvailableActions()
     {
         IQueryable<ActionType> actionTypeQuery = _repository.Query<ActionType>();
         return actionTypeQuery.Where(x => x.Name == "debug").AsEnumerable();
     }

     #endregion
}

and I was having a hard time figuring out how to stub or mock the

actionTypeQuery.Where(x => x.Name == "debug")

part.

Here’s what I got so far:

[TestFixture]
public class ServiceClassTester
{
    private ServiceClass _service;
    private IRepository _repository;
    private IQueryable<ActionType> _actionQuery;
    [SetUp]
    public void SetUp()
    {
        _repository = MockRepository.GenerateMock<IRepository>();
        _service = new ServiceClass(_repository);
    }

    [Test]
    public void heres_a_test()
    {
        _actionQuery = MockRepository.GenerateStub<IQueryable<ActionType>>();

        _repository.Expect(x => x.Query<ActionType>()).Return(_actionQuery);
        _actionQuery.Expect(x => x.Where(y => y.Name == "debug")).Return(_actionQuery);

        _service.GetAvailableActions();

        _repository.VerifyAllExpectations();
        _actionQuery.VerifyAllExpectations();
    }

}

[Note: class names have been changed to protect the innocent]

But this fails with a System.NullReferenceException at

_actionQuery.Expect(x => x.Where(y => y.Name == "debug")).Return(_actionQuery);

So my question is:

How do I mock or stub the IQueryable.Where function with RhinoMocks and get this test to pass?

If my current setup won’t allow me to mock or stub IQueryable, then give a reasoned explanation why.

Thanks for reading this epically long question.

Answer 1

I initially wanted to mock out calls like ‘IQueryable.Where(Func)’ too but I think it is testing at the wrong level. Instead in my tests I just mocked out IQueryable and then check the result:

// Setup a dummy list that will be filtered, queried, etc
var actionList = new List<ActionType>()
{
    new ActionType() { Name = "debug" },
    new ActionType() { Name = "other" }
};
_repository.Expect(x => x.Query<ActionType>()).Return(actionList);

var result = _service.GetAvailableActions().ToList();

// Check the logic of GetAvailableActions returns the correct subset 
// of actionList, etc:
Assert.That(result.Length, Is.EqualTo(1));
Assert.That(result[0], Is.EqualTo(actionList[0]);

_repository.VerifyAllExpectations();