MOQ returning null. [mock concrete class method] - unit-testing

Question

[using Moq]
I am trying to mock a concrete class and mock a virtual method "Get()" of that class. When testing a method "GetItemsNotNull()" I always get returned null, instead of the return of the mocked function.
Here is the code
//SomeClasses.cs
namespace MoQExamples
{
public abstract class Entity
{
}
public class Abc : Entity
{
}
public interface IRepository<T> where T : Entity
{
IQueryable<T> Get();
}
public class Repository<T> : IRepository<T> where T : Entity
{
private readonly ISession _session;
public Repository()
{
_session = null;
}
public Repository(ISession session)
{
_session = session;
}
protected ISession CurrentSession
{
get { return _session; }
}
public virtual IQueryable<T> Get()
{
return CurrentSession.Query<T>();
}
}
public interface IAbcRepository
{
Abc GetItemsNotNull();
}
public class AbcRepository : Repository<Abc>, IAbcRepository
{
public Abc GetItemsNotNull()
{
return Get().FirstOrDefault(abc => abc !=null);
}
}
}
and here are the test class
namespace MoQExamples
{
[TestFixture]
public class SomeClassesTest
{
private readonly Mock<AbcRepository> _abcRepositoryMock = new Mock<AbcRepository>(MockBehavior.Strict) { CallBase = true };
[SetUp]
public void SetupTest()
{
_abcRepositoryMock.Setup(x => x.Get()).Returns(Get);
}
public IQueryable<Abc> Get()
{
return (new List<Abc>() { new Abc() }) as IQueryable<Abc>;
}
[Test]
public void TestGetItemsNotNull()
{
Assert.IsNotNull(_abcRepositoryMock.Object.GetItemsNotNull());
}
}
}
the assert alays fails..instead of returning the SomeClassesTest.Get()
thanks for advance guys!

Answer 1

I suspect this is the problem:
return (new List<Abc>() { new Abc() }) as IQueryable<Abc>;
List<T> doesn't implement IQueryable<T>, so this will always return null. Call AsQueryable to convert it instead:
return new List<Abc>().AsQueryable();
As an aside, this is a reason to prefer casts over as in most situations: if you'd just cast to IQueryable<Abc>, you'd have received an exception at the line which was really causing the problem. You should only use as when it's not a bug for the conversion to "fail". An as operator should almost always be followed by a nullity test.
(Note that this behaviour in itself has nothing to do with mocking or Moq. It's just the behaviour of the as operator...)