C# Dev Kit Test Explorer does not discover tests for .slnx solution, while dotnet test on the same .slnx succeeds

[moni-dips]

Describe the Issue

If I add an equivalent legacy .sln for the same projects, Test Explorer starts showing the tests.

So this does not appear to be a .NET SDK or test adapter problem. It looks like a C# Dev Kit / VS Code project-loading or test-discovery issue specific to .slnx.

Steps To Reproduce

1. Create a solution with the current SDK so it defaults to .slnx:
2. Create a class library and xUnit test project:
3. Add both projects to the .slnx:
4. Confirm CLI test discovery works:
5. Open the folder in VS Code with C# Dev Kit enabled.
6. Observe that Test Explorer does not discover the tests.
7. Create an equivalent legacy .sln and add the same projects:
8. Reopen or switch to the .sln.
9. Observe that Test Explorer now discovers the tests.

Expected Behavior

If C# Dev Kit can open the .slnx and dotnet test Repro.slnx succeeds, Test Explorer should also discover tests from that solution.

Environment Information

• OS: Windows
• Extension version: 3.10.4

detailed version info:

Version: 1.113.0 (user setup)
Commit: cfbea10c5ffb233ea9177d34726e6056e89913dc
Date: 2026-03-24T15:07:18+01:00
Electron: 39.8.3
ElectronBuildId: 13620978
Chromium: 142.0.7444.265
Node.js: 22.22.1
V8: 14.2.231.22-electron.0
OS: Windows_NT x64 10.0.26100

[peterwald]

I'm not able to reproduce this issue. I followed the steps above with the same versions of C# Dev Kit and it discovered the tests just fine.

@moni-dips C# Dev Kit should have no issue with slnx files or treat them any differently than sln files. Do you have any errors in the Output window under "C# Dev Kit - Test Explorer" that might provide more details?

[moni-dips]

couldn't reproduce exactly as written now, but when I right click the slnx and select run tests, I get a popup saying No tests found in the selected file or folder

[peterwald]

That is a function of the way VS Code works. Because we have the ability to handle tests, vs code enables that command which looks to see if there are any tests that have been registered as being in that file (which there won't be), so it returns that error. If you right click on a .cs file that contains tests, then it should run those tests.

[moni-dips]

well that is a different bug, then, it should be the same as running dotnet test on the solution, I think.