xUnit tests are not discovered (and run) in a .Net9 UWP application

[vgromfeld]

Description

I've converted an UWP test application using xUnit to .Net 9 + AOT.
The xUnit tests are not discovered (and not run).

Steps To Reproduce

1. Create an UWP test application
2. Import xUnit nuget package
3. Convert the project to a .Net 9 project
4. Add an MSTest class:

[TestClass]
public class msUnitTest
{
    [TestMethod]
    public void Test()
    {
        var a = 10;
        Assert.AreEqual(10, a);
    }
}

5. Add an xUnit test class

public class xUnitTest
{
    [Fact]
    public void Test()
    {
        var a = 10;
        a.Should().Be(10);
    }
}

7. Run the tests

Only the msTest.Test test is run.

Expected Behavior

All the tests should run.

Version Info

TargetFramework = net9.0-windows10.0.26100.0
Microsoft.NET.Test.Sdk = 17.14.0-preview-25107-01
MSTest = 3.8.2
xunit = 2.9.3
xunit.runner.visualstudio = 3.0.2

Additional Context

Sample test application: UnitTests.zip

[Sergio0694]

As a sanity check, can you verify whether they work with just MSTest 3.8.2 and that preview test SDK?
I'm interested in seeing if on your machine this is just an issue specific to xUnit. If so, it's likely an issue on their end.

[vgromfeld]

I've tried with a basic xUnit test project. And everything stops to work as soon as I'm adding <Platforms>x86;x64;arm64</Platforms>. It seems to be more an AOT+xUnit issue than a csWinRT issue 🤔

[Sergio0694]

Can you do a sanity check with MSTest as well? I'd like to understand if it's just xUnit here causing issues.
Here's what's working for me:

<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.0-preview-25107-01" />
<PackageReference Include="MSTest" Version="3.8.2" />

[vgromfeld]

If I just have mstest tests, everything is working

[Sergio0694]

Ah, I see. This might be a bug in xUnit then, they might need to do some tweaks to make UWP .NET 9 work. Perhaps we should open an issue in their repo and link it to this one, so they can track it? In the meantime, is this blocking you, or could you move to MSTest so that your test can keep working without needing them to update things on their end?

[vgromfeld]

I've opened xunit/xunit#3219 in xUnit repo.
I'd like to avoid to convert all our (UWP) tests to MSTests, we have too many of them 😅