BackgroundService_MultipleExceptions_ThrowsAggregateException is racy on macOS

[danmoseley]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1336322
Build error leg or test failing: Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException
Pull request: #125555

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": "Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException",
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1336322
Error message validated: [Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 3/15/2026 10:01:37 PM UTC

Report

Build	Definition	Test	Pull Request
1336322	dotnet/runtime	Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException	#125555

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
1	1	1

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Tagging subscribers to this area: @dotnet/area-extensions-hosting
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[VincentBu]

Failed in: runtime-coreclr libraries-jitstressregs 20260315.1

Failed tests:

net11.0-windows-Release-arm64-jitstressregs3-Windows.11.Arm64.Open
- Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException

Error message:

Assert.Equal() Failure: Values differ
Expected: 3
Actual:   2

Stack trace:

   at Microsoft.Extensions.Hosting.Tests.BackgroundServiceExceptionTests.BackgroundService_MultipleExceptions_ThrowsAggregateException() in /_/src/libraries/Microsoft.Extensions.Hosting/tests/UnitTests/BackgroundServiceExceptionTests.cs:line 148
--- End of stack trace from previous location ---