Functional regression in `Moq.AutoMock` 4.0.0

[nil4]

A regression is observed upgrading a project from v3.6.1 to v4.0.0 -- code that worked fine with the earlier version throws unexpectedly with the new one.

Steps to reproduce

> dotnet --version
10.0.201

> dotnet new console
> dotnet package add Microsoft.Extensions.Options
> dotnet package add Moq.AutoMock --version 3.6.1

Replace Program.cs with:

using Microsoft.Extensions.Options;
using Moq;
using Moq.AutoMock;

static class Program
{
    static void Main()
    {
        var mocker = new AutoMocker();
     
        var options = mocker.GetMock<IOptions<TestOptions>>();
        options.SetupGet(x => x.Value).Returns(new TestOptions());

        var serviceProvider = mocker.GetMock<IServiceProvider>();
        serviceProvider.Setup(x => x.GetService(It.IsAny<Type>()))
            .Returns<Type>((serviceType) => mocker.GetMock(serviceType).Object);
    }

    sealed class TestOptions;
}

Run the program and observe that it builds and executes without issues.

Upgrade the Moq.AutoMock package to version 4.0.0 and run the program again.

Expected behavior

Mocking behaves consistently with the earlier version.

Observed behavior

Unhandled exception. System.ArgumentException: Registered service `Moq.AutoMock.AutoMocker` was not a mock
   at Moq.AutoMock.AutoMocker.GetMockImplementation(Type serviceType, Boolean enablePrivate)
   at Moq.AutoMock.AutoMocker.GetMock(Type serviceType, Boolean enablePrivate)
   at Moq.AutoMock.AutoMocker.GetMock(Type serviceType)
   at Moq.AutoMock.AutoMocker.GetMock[TService]()
   at Program.Main() in Program.cs:line 14

Is this a breaking change in version 4.0.0? I couldn't find change logs or release notes for v4, so it's possible that I had overlooked something relevant. Would appreciate any insight into addressing this new behavior.

[Keboo]

Hi @nil4

Thank you for the great write up. The issue was with PR #441. This was not an intentional side affect of that. AutoMocker contains a set of resolvers that will attempt to resolve requested types when the type is not already cached. In this case the SelfResolver was matching the AutoMocker instance itself because it implements IServiceProvider. However, because it was requested with GetMock the instance does not cast to a Mock<IServiceProvider> causing the exception you were seeing.

There are a few options.

1. Directly create and inject the mock. This works because the cached mocks are checked first mocker.Use(new Mock<IServiceProvider>());
2. Simply remove the setup. Because it appears that you are simply wanting AutoMocker to resolve IServiceProvider parameters, and then on all calls to that service provider return turn mocks. You could simply just remove mocker.GetMock<IServiceProvider>(); from your code and it will continue to work normally.
3. I am rolling out 4.0.1 right now which has a fix for this issue.

[nil4]

Thank you for the quick reaction -- much appreciated, @Keboo! The snippet above is just a minimal repro excerpt; in the actual code, the IServiceProvider is later built up upon significantly with other mocks. Looking forward to 4.0.1 being available. 👍🏻

[Keboo]

@nil4 should be out on NuGet now! Let me know how it works for you.

[nil4]

Looking good -- thanks again @Keboo!

[Keboo]

Awesome. Happy coding!