AddRangeAsync xunit .net core error

[zaiboot]

Running on:

• VS2017
• .net core 1.1
• moq 4.7.1
• xunit 2.2.0-beta5-build3474
• xunit.runner.visualstudio : 2.2.0-beta5-build1225

I have the following code on my repositoryfile.cs

public async Task<int> AddSales(IList<SomeModel> mode)
{
    await Context.DBSet.AddRangeAsync(model);
    return await Context.SaveChangesAsync();
}

And the following test:

[Fact]
public async void AddSalesTest()
{
    var expected = 1;
    var sales = new List<SomeModel>
    {
        new SomeModel{ ... }
    };
    _context.Setup(c => c.DBSet.AddRangeAsync(It.IsAny<List<SomeModel>>(), It.IsAny<CancellationToken>()));
    _context.Setup(c => c.SaveChangesAsync(It.IsAny<CancellationToken>())).ReturnsAsync(expected);
    var system = GetSystem();
    var actual = await system.AddSales(sales);
    Assert.Equal(expected, actual);
}

Getting the following error:

Message: Moq.MockException : DbSet`1.AddRangeAsync([Reporting.DAL.Models.SomeModel], System.Threading.CancellationToken) invocation failed with mock behavior Strict.
Invocation needs to return a value and therefore must have a corresponding setup that provides it.

Seems like Moq doesnt support mocking Task vs Task<OfSomething>.

Any ideas on this? If you need more info I can set up a git repo to show the error in a more easy way.

Thanks

[stakx]

@zaiboot: Your code won't compile since it's incomplete so it's hard to reproduce your issue, but I guess this part of the error message is a sufficient hint at what is going wrong here:

….AddRangeAsync(…) invocation failed with mock behavior Strict.
Invocation needs to return a value and therefore must have a corresponding setup that provides it.

This tells you that the first of your two setups (the one involving AddRangeAsync) is incomplete; it is lacking a .Returns. As I understand it, MockBehavior.Strict requires every .Setup to have a .Returns:

_context.Setup(c => c.DBSet.AddRangeAsync(It.IsAny<List<SomeModel>>(), It.IsAny<CancellationToken>()));

If you add a .Returns(…), the error should go away:

_context.Setup(c => c.DBSet.AddRangeAsync(…))
        .Returns((List<SomeModel> _, CancellationToken __) => Task.FromResult(true));

(Tried this the latest version of Moq, which is 4.7.25.)

[stakx]

I do wonder, though, whether there should be a .SetupAsync(Expression<Func<T, Task>>) that doesn't require a .Returns.

• On the one hand, for methods returning a value there must be a .Returns — and async methods (should) return a Task...
• On the other hand, methods returning Task are really the asynchronous counterpart to void methods, and those do not require a .Returns.

[stakx]

I am closing this for now, since we have no working repro code and the reported error is quite possibly due to incorrect usage (see this comment further above).

Regarding my previous comment just above, I think this would be better tracked in #384.

@zaiboot: If the above does not help you, please report back and we take another look at your issue.

[stakx]

This is quite likely a minimal repro code example for this issue:

public interface IFoo
{
    Task DoAsync();
}

var mock = new Mock<IFoo>(MockBehavior.Strict);
mock.Setup(m => m.DoAsync());
await mock.Object.DoAsync();

As noted above, one could argue that there should be a Mock<T>.SetupAsync(Expression<Func<T, Task>>) method such that async methods can be set up without specifying .Returns.