TestTfmsInParallel: false setting is not works after update to xUnit v3

[filzrev]

I'm using <TestTfmsInParallel>false</TestTfmsInParallel> setting to disable parallel execution between TargetFrameworks.
But after updating to xUnit v3.
It seems not works as expected.

Reproduce steps

1. Create xUnit v2 based project. And update packages to latest version (xUnit: 2.9.2/ xunit.runner.visualstudio: 3.0.0)
2. Modify .csproj with following changes.
   2.1. Set <TargetFrameworks>net8.0;net9.0<TargetFrameworks>
   2.2. Set <TestTfmsInParallel>false</TestTfmsInParallel>
3. Insert Thread.Sleep(5000) to unit test code.
4. Run tests on Test Explorer and confirms tests is isolated between target frameworks.
5. Modify .csproj to use xUnit v3 (<PackageReference Include="xunit.v3" Version="1.0.0" />)
6. Run tests on Test Explorer and confirms tests is executed in parallel.

Environment
I've confirmed it can be reproduced on following environment.

• Visual Studio 2022 Version 17.12.0 (With preview feature Use testing platform server mode enabled)
• Visual Studio 2022 Version 17.13.0 Preview 2.0

[filzrev]

I've confirmed same issue can be reproduced when using MSTest.Sdk/3.6.3.

So it this issue might be caused by Microsoft.Testing.Platform or VS Test Explorer side.
I've created issue to testfx repository microsoft/testfx#4392

[bradwilson]

I agree, especially because I had no idea TestTfmsInParallel even existed before today. 😂

[filzrev]

As stated on microsoft/testfx#4392 (comment) comment.
It seems be caused by VS Test Explorer side problems.

Currently it's tracked on following ticket.
https://developercommunity.visualstudio.com/t/TestTfmsInParallel:false-does-not-work-w/10817302

I'll close this issue when it's resolved on latest VS preview.