EF Core 3.1: New Overrides

[JakenVeina]

Protip: When supporting EF Core 3.1, mocked DbSet<> objects need to additionally override the newly-added methods .AsQueryable() and .AsAsyncEnumerable() (which simply return this;) within BuildMockDbSet() calls.

Anyone who (like me) was using the .AsQueryable() extension method upon a DbSet<> in production code will, after upgrade to 3.1, be calling the methods upon DbSet<> instead. In my case, this meant that instead of getting a cast of the DbSet<> to IQueryable<> I was getting an auto-generated default implementation from Moq's DefaultValueProvider, which is basically Array.Empty<T>.AsQueryable().

[romantitov]

@JakenVeina thank you for the feedback.
Not sure that the issue is clear for me.
I've tried to run tests in the solution with EF Core 3.1.1, and all tests is green. Could you provide an example of failed test to reproduce the issue?

[JakenVeina]

Basically, I was doing

var query = _context.Set<MyEntity>()
    .AsQueryable();

if(...)
    query = query.Where(...);

in a method under test. The .AsQueryable() call was just my way of casting to IQueryable<T> so I can re-use the variable query.

The change is that in 3.0, .AsQueryable() resolves to the LINQ extension method, while in 3.1, it resolves to the new method that was added to DbSet<>. So, when I've configured the test to have _context.Set<MyEntity>() return a mocked DbSet<> the behavior suddenly changed. It took me a couple hours to figure out why the set was coming back empty, and it was that Mock<DbSet<>> specifically has logic to return something other than null for methods returning IQueryable<T> It just builds a queryable out of an empty array.

Easily worked around on my end, once I realized what the issue is, but this seems like a good candidate to be added to the .Setup() calls that MockQueryable does for you.

[romantitov]

The issue fixed in release 3.1.1

[likemike91]

Is that also fixed for NSubstitute?
Unfortunately I get the same error when using NSubstitute and I didn't see the fix in the code of the NSubstitute extension?

[romantitov]

@likemike91 could you open a new issue if you still facing with the error

[krilllind]

@likemike91 Created a new ticket and PR. Hopefully we can get this fixed 👍