MTP (Microsoft Testing Platform) with NUnit causes CI hangs

[jas88]

Summary

Microsoft Testing Platform (MTP) with NUnit3TestAdapter 6.0.1 causes the test process to hang indefinitely after all tests complete. Tests pass successfully, but MTP never exits, requiring external termination.

Details

• NUnit3TestAdapter: 6.0.1
• NUnit: 4.4.0
• Microsoft.NET.Test.Sdk: 18.0.1
• .NET SDK: 10.0.101

Observed Behavior

1. Tests run and complete successfully (e.g., 1998 passed, 182 skipped)
2. NUnit reports "Test execution complete"
3. MTP continues running, printing status updates every 3 seconds
4. Process never exits - must be killed externally (timeout, Ctrl+C, etc.)

Workarounds Tried (None Worked)

• [assembly: NonParallelizable] - Disabling parallel tests
• --hangdump --hangdump-timeout 2m - HangDump extension (doesn't trigger because tests complete, no "inactivity")
• Preview packages Microsoft.Testing.Platform.MSBuild 2.1.0-preview.26076.3 with Linux HangDump fix
• Parsing test output to detect pass/fail and allowing timeout to kill process

Related Issues

• nunit/nunit3-vs-adapter#1282 - MTP + parallel tests + cancellation hang
• nunit/nunit3-vs-adapter#1361 - dotnet test using MTP cannot be cancelled
• microsoft/testfx#6776 - MTP timeout doesn't abort hanging tests

Current Resolution

Reverted to VSTest mode by removing MTP configuration from global.json. This allows CI to pass.

Future Action

Re-evaluate MTP when the NUnit adapter issues are resolved. The MTP infrastructure offers benefits (HangDump, better diagnostics), but the shutdown hang makes it unusable for CI.