IDbAsyncEnumerable not implemented

Question

I am trying to make a FakeDbContext with a FakeDbSet for unit testing.

But I get the following error (see below). I am extending DbSet so normally IDbAsyncEnumerable

Answer 1

Your scenario is explicitly mentioned in the link provided with the exception message (http://go.microsoft.com/fwlink/?LinkId=287068). The missing ingredient is the IDbAsyncQueryProvider that you should return from your Provider property.

Just navigate through the link to arrive at the boilerplate implementation.

Little I can add, I'll just quote the essential phrase:

In order to use asynchronous queries we need to do a little more work. If we tried to use our Moq DbSet with the GetAllBlogsAsync method we would get the following exception:

System.InvalidOperationException: The source IQueryable doesn't implement IDbAsyncEnumerable. Only sources that implement IDbAsyncEnumerable can be used for Entity Framework asynchronous operations. For more details see http://go.microsoft.com/fwlink/?LinkId=287068.

In order to use the async methods we need to create an in-memory DbAsyncQueryProvider to process the async query. Whilst it would be possible to setup a query provider using Moq, it is much easier to create a test double implementation in code. The code for this implementation is as follows:

etc...