[Tests] LogsPipelineUnitTests TestLogsPipeline fails with Assert.Equal() Failure

[mdh1418]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1483640
Build error leg or test failing: Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline

{
  "ErrorMessage": "Assert.Equal() Failure: Values differ\\nExpected: 5\\nActual:",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Assert.Equal() Failure: Values differ\nExpected: 5\nActual: 2
This line might be

diagnostics/src/tests/Microsoft.Diagnostics.Monitoring.EventPipe/LogsPipelineUnitTests.cs

Line 68 in 33fbc95

Assert.Equal(5, logger.LogRecords.Count);

The test failed on an unrelated PR on MacOS_x64_Debug Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline(config: projectk.sdk.prebuilt.10.0.2) https://dev.azure.com/dnceng-public/public/_build/results?buildId=1224196&view=ms.vss-test-web.build-test-results-tab&runId=33919198&resultId=100117&paneView=debug

The console output looks like

[12/8/2025 8:52:57 PM] Test runner created
Running Process: /Users/runner/work/1/s/artifacts/dotnet-test/dotnet --fx-version 10.0.2 /Users/runner/work/1/s/artifacts/bin/EventPipeTracee/Debug/net10.0/EventPipeTracee.dll 12a52368-197c-48b4-8895-e208ec15f021 LoggerRemoteTest
Working Directory: 
Additional Environment Variables: DOTNET_ROOT=/Users/runner/work/1/s/artifacts/dotnet-test
{
    [00:00.313] 10921 Successfully started process
    [00:00.316] 10921 WaitForTracee
    00:00.277: 10921 EventPipeTracee: DiagMetrics False UseActivitySource False
    00:00.280: 10921 EventPipeTracee: DuplicateNameMetrics False
    00:00.280: 10921 EventPipeTracee: start process
    00:00.280: 10921 EventPipeTracee: connecting to pipe
    00:00.280: 10921 EventPipeTracee: connected to pipe
    [00:00.318] 10921 WaitForTracee: DONE
    00:00.668: 10921 EventPipeTracee: 12/8/2025 8:52:58 PM Awaiting start
    [00:01.555] 10921 WakeupTracee
    [00:01.555] 10921 WakeupTracee DONE
    [00:01.555] 10921 WaitForSignal
    00:01.519: 10921 12/8/2025 8:52:59 PM Starting test body '42'
    00:01.568: 10921 EventPipeTracee: signal end of test data
    [00:01.605] 10921 WaitForSignal DONE 31
    00:01.569: 10921 12/8/2025 8:52:59 PM Awaiting end
    [00:01.949] 10921 WakeupTracee
    [00:01.949] 10921 WakeupTracee DONE
    00:01.913: 10921 EventPipeTracee 12/8/2025 8:52:59 PM Ending remote test process '42'
}
    [00:02.050] 10921 Disposing
    [00:02.050] 10921 WakeupTracee
Process 10921 exited 0 (00:02.014 elapsed)

    [00:02.051] 10921 WakeupTracee DONE
    [00:02.051] 10921 WaitForExitAsync
    [00:02.051] 10921 WaitForExitAsync DONE

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1483640
Error message validated: [Assert.Equal() Failure: Values differ\nExpected: 5\nActual:]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 6/27/2026 12:21:20 AM UTC

Report

Build	Repository	Test	Pull Request
1589773	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#6018
1588331	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5993
1583728	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#6000
1582409	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#6010
1582271	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#6004
1579729	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5980
1578684	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5991
1577892	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5980
1571666	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5981
1569701	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5981
1565590	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5976
1565556	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5976
1565330	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5976
1561156	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5970
1556588	dotnet/diagnostics	Microsoft.Diagnostics.Monitoring.EventPipe.UnitTests.LogsPipelineUnitTests.TestLogsPipeline	#5966

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	2	15

[hoyosjs]

This is actually a runtime issue: dotnet/runtime#127681. Added a workaround for now in #5767

[hoyosjs]

Looks like this is still hitting pretty hard