Target NetCurrent for Microsoft.DotNet.XUnitConsoleRunner test host

[steveisok]

Note

This pull request was drafted with assistance from GitHub Copilot (AI-generated content).

Summary

Change Microsoft.DotNet.XUnitConsoleRunner (xunit.console.dll) to target $(NetCurrent) instead of $(NetMinimum). The XUnitConsoleRunner is a test host that runs test assemblies built against the current .NET TFM, so its host runtime must also be the current TFM.

Background

#16795 ("Downgrade TFM to NetMinimum") changed several Arcade projects from $(BundledNETCoreAppTargetFramework) to $(NetMinimum) to decouple Arcade from the installed .NET SDK. That change is appropriate for build-time MSBuild tasks, but the Microsoft.DotNet.XUnitConsoleRunner project produces xunit.console.dll, the test host executable shipped via the Microsoft.DotNet.XUnitConsoleRunner package and consumed by Microsoft.DotNet.XHarness.TestRunners.Xunit, RemoteExecutor, etc.

For RemoteExecutor, #16795 also added <RollForward>Major</RollForward> as mitigation. No equivalent mitigation was added for XUnitConsoleRunner, and RollForward=Major would not actually have helped here — once the .NET 10 host is selected, even forward-rolling can't load a test assembly that references members only present in net11's BCL.

Repro / impact

Consumer: dotnet/runtime#128648 (a routine VMR backflow PR). The Wasm.Build.Tests Helix work items fail with:

TypeLoadException: Could not load type 'Wasm.Build.Tests.WasmTemplateTestsBase'
from assembly 'Wasm.Build.Tests, Version=11.0.0.0, ...' because the format is invalid.

23 of 24 work items fail per CLR-on-WASM job. Failing build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1438863. Baseline passing main build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1438570.

Smoking-gun evidence

I diffed the entire Helix payload between a passing main build and the failing PR build (210 DLLs). Only six differ; five are inert (MVID-only or attribute-blob deltas). The substantive change is in xunit.console.dll:

-.assembly extern System.Runtime { .ver 11:0:0:0 }
+.assembly extern System.Runtime { .ver 10:0:0:0 }
...
-.custom instance void [System.Runtime]System.Runtime.Versioning.TargetFrameworkAttribute::.ctor(string)
-   = ( ... ".NETCoreApp,Version=v11.0" ... )
+.custom instance void [System.Runtime]System.Runtime.Versioning.TargetFrameworkAttribute::.ctor(string)
+   = ( ... ".NETCoreApp,Version=v10.0" ... )

And the host runtimeconfig:

	tfm	framework.version
main (passing)	net11.0	11.0.0-preview.5.26227.104
PR (failing)	net10.0	10.0.0

The .NET 10 host is then asked to load a test assembly that references System.Runtime, Version=11.0.0.0 and types/members only present in net11 → TypeLoadException.

Fix

-    <TargetFramework>$(NetMinimum)</TargetFramework>
+    <!-- Target NetCurrent so the test host can load test assemblies built against
+         the current .NET TFM. Using NetMinimum here causes TypeLoadException
+         "format is invalid" when loading newer-TFM test assemblies because the
+         minimum .NET runtime is selected and cannot resolve newer BCL members. -->
+    <TargetFramework>$(NetCurrent)</TargetFramework>

This preserves #16795's "decouple from the SDK" intent — NetCurrent is just an Arcade property, not the SDK's bundled TFM, and ref packs are NuGet-restored.

Notes / open questions

• Validation against dotnet/runtime (Wasm.Build.Tests) will confirm the fix; happy to chase that with an arcade insertion once this is in.
• Did not touch RemoteExecutor — its RollForward=Major mitigation may also be insufficient for runtime/test-assembly cases, but that's a separate investigation.
• Should this be considered for a NetMinimum-targeted release branch too, if any consumer depends on it for test execution?

Refs

• Regression source: Downgrade TFM to NetMinimum #16795 (commit 98d7ce0)
• Failing consumer: [main] Source code updates from dotnet/dotnet runtime#128648

[Copilot]

Pull request overview

Reverts Microsoft.DotNet.XUnitConsoleRunner.csproj from $(NetMinimum) back to $(NetCurrent) so the xUnit console test host runs on the current .NET TFM and can load test assemblies built against newer BCL members. This addresses a regression from #16795 where the NetMinimum (net10.0) host could not load net11.0 test assemblies, causing TypeLoadException in consumers such as dotnet/runtime Wasm.Build.Tests.

Changes:

• Change TargetFramework from $(NetMinimum) to $(NetCurrent) for the xUnit console runner test host.
• Add an explanatory comment noting why NetMinimum is unsuitable for this test-host project.

[ViktorHofer]

Requiring XUnitConsoleRunner to target and run on NetCurrent is a dotnet/runtime specific requirement, other repos run with older versions of .NET. This is fine to take if you add to NetMinimum, instead of replacing it. Other test host runner also multi-target (i.e. xunit.console or vstest).

[ViktorHofer]

FWIW this whole project would ideally get deleted after most consumers switched to xunit.v3 which has in-built support (or via MTP) to run the tests and doesn't need a separate runner assembly.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.