How do I mock IQueryable<T>

Question

I am creating a repository that exposes IQueryable. What is the best way to mock this out for my unit testing?

Since I am using RhinoMocks for the rest of my mock objects, I tried to do the following:

IQueryable<MyObject> QueryObject = 
    MockRepository.GenerateStub<IQueryable<MyObject>>();

This doesn't work though so I tried doing this:

IQueryable<MyObject> QueryObject = 
    (new List<MyObject> { new MyObject() }).AsQueryable();

Is there a better way to do this, or have any other mocking frameworks built support for IQueryable in?

My repository interface looks like this:

public interface IRepository<T> where T : TableServiceEntity
{
    IQueryable<T> Table { get; }
    void Attach(T existingItem);
    void Delete(T itemToDelete);
    void Insert(T newItem);
    T Load(string partitionKey, string rowKey);
    IEnumerable<T> Load(string partitionKey);
    IEnumerable<T> Query(IQueryable<T> query);
    IEnumerable<T> Last(int count);
    T Last();
    void Update(T item);
}

Here is the method that I want to test:

public Post LoadPost(int year, int month, int day, string slug)
{
    var query = from p in _blogRepository.Table
                where 
                    p.PartitionKey == Key.Partition(year, month, day) 
                    && p.Slug == slug
                select p;

    var posts = _blogRepository.Query(query.Take(1));

    return posts.First();
}

Then here is the test as I have it right now that will test LoadPost.

[Fact]
public void LoadWillRetrieveByPartitionKeyAndRowKeyWhenUsingUriFormat()
{
    Repository
        .Stub(x => x.Query(Arg<IQueryable<Post>>.Is.Anything))
        .Return(new List<Post> {_post});

    var result = Service.LoadPost(
                            _post.Year(),
                            _post.Month(), 
                            _post.Day(), 
                            _post.Slug);

    Assert.NotNull(result);
}

The code is taken from my AzureBlog project.

Answer 1

I usually do exactly what you ended up doing in your test. When writing my tests I assume that the .Net library classes work correctly and don't contain bugs, so I can use them in the tests. When I need a test list, collection, queryable, dictionary, etc. I just create the real thing and populate with test data. It makes the tests much more readable and quicker to write, and to be honest the risk is non-existent.