How to unit test async methods of Entity Framework with a multiple clauses

Question

I'm trying to unit test an async method in EF 6.0.2 with Moq 4.0.10827 and I'm getting blocked in what appears to be a casting issue.

The following works fine:

public async Task<List<Testimonial>> GetByEventIdAsync(int eventId)
{
    var query = from t in _context.Testimonials
                orderby t.Ordinal
                select t;
    var result = query
        .ToListAsync()
        .ConfigureAwait(false);
    return await result;
}

but the following breaks (added a where clause)

public async Task<List<Testimonial>> GetByEventIdAsync(int eventId)
{
    var query = from t in _context.Testimonials
                where t.EventId == eventId
                orderby t.Ordinal
                select t;
    var result = query
        .ToListAsync()
        .ConfigureAwait(false);
    return await result;
}

I did some debugging and found the following

var q1 = _context.Testimonials; // Type = Castle.Proxies.IDbSet`1Proxy_1
var q2 = q1.Where(t => t.EventId == eventId); // Type = TestDbAsyncEnumerable`1 (from linked code)
var q3 = q2.OrderBy(o => o.Ordinal); // Type = System.Linq.EnumerableQuery`1

Why is the class double disappearing? And how do I fix it?

UPDATE: I also found that if I add the where back and remove the orderby, that also works, so the issue seems to be having multiple clauses.

Answer 1

Finally found the answer here.

IQueryable needed to be added like so:

public class TestDbAsyncEnumerable<T> 
    : EnumerableQuery<T>, IDbAsyncEnumerable<T>, IQueryable