[ci-scan] Test failure: System.Net.Tests.HttpResponseStreamTests.Write_ContentToClosedConnectionSynchronously_ThrowsHttpListener [Content truncated due to length]

[github-actions]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1494308
Build error leg or test failing: maccatalyst-x64 Release AllSubsets_NativeAOT - System.Net.HttpListener.Tests

Error Details

On the Apple NativeAOT library-test legs (maccatalyst / iossimulator AllSubsets_NativeAOT), HttpResponseStreamTests.Write_ContentToClosedConnectionSynchronously_ThrowsHttpListenerException fails its Assert.Throws check. Writing to an already-closed connection does not raise on the Darwin/Apple socket stack, so the expected HttpListenerException is never thrown:

[FAIL] System.Net.Tests.HttpResponseStreamTests.Write_ContentToClosedConnectionSynchronously_ThrowsHttpListenerException(ignoreWriteExceptions: False)
Assert.Throws() Failure: No exception was thrown
Expected: typeof(System.Net.HttpListenerException)
   at System.Net.Tests.HttpResponseStreamTests.<Write_ContentToClosedConnectionSynchronously_ThrowsHttpListenerException>d__20.MoveNext() in /_/src/libraries/System.Net.HttpListener/tests/HttpResponseStreamTests.cs:line 449

The test carries [ActiveIssue(".../issues/21590", TestPlatforms.OSX | TestPlatforms.FreeBSD)], but that skip does not include TestPlatforms.MacCatalyst, so it runs and fails on the maccatalyst NativeAOT leg. NativeAOT library tests on Apple mobile were newly enabled by #125437 (merged 2026-07-02); the failure first appears on build 1492684 (2026-07-03) and reproduces on follow-up build 1494829. The ...Asynchronously... sibling variant of the same behavioural difference is catalogued in the Apple-mobile NativeAOT tracker #126697. Sibling Apple-NativeAOT library-test failures from the same source build are tracked by #130253 and #130254.

First build it occurred: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1492684

Related: #126697

Error Message

{
  "ErrorMessage": [
    "[FAIL] System.Net.Tests.HttpResponseStreamTests.Write_ContentToClosedConnectionSynchronously_ThrowsHttpListenerException",
    "Expected: typeof(System.Net.HttpListenerException)"
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

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Report

Build	Repository	Test	Pull Request
1496784	dotnet/runtime	System.Net.HttpListener.Tests.WorkItemExecution	#130292

Summary

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

[JulieLeeMSFT]

@kotlarmilos, please activate area bot for these new issues.

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Tagging subscribers to this area: @karelz, @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

[github-actions]

Workflow artifact: ci-fix
Artifact kind: handoff
Linked KBE: #130278

Note

AI/Copilot-generated root-cause hand-off (ci-failure-fix). No automated code change was produced: the only in-bounds options would be to extend an [ActiveIssue] skip to MacCatalyst (muting) or to change Darwin socket behavior (out of bounds), so I am looping in owners instead.

Root cause (read-only analysis)

On the Apple NativeAOT library-test legs (maccatalyst / iossimulator AllSubsets_NativeAOT, build 1494308), System.Net.Tests.HttpResponseStreamTests.Write_ContentToClosedConnectionSynchronously_ThrowsHttpListenerException fails:

Assert.Throws() Failure: No exception was thrown
Expected: typeof(System.Net.HttpListenerException)
   at .../HttpResponseStreamTests.cs:line 449

The test writes to an already-closed connection and expects an HttpListenerException. On the Darwin/Apple socket stack the synchronous write to a closed connection does not raise, so no exception is thrown and the assert fails.

The test already carries [ActiveIssue(".../issues/21590", TestPlatforms.OSX | TestPlatforms.FreeBSD)], but that platform mask does not include TestPlatforms.MacCatalyst, so it runs on the maccatalyst leg. This is the same behavioral difference already catalogued (async sibling) in #126697.

Both conceivable changes are out of scope for this workflow:

• Extending the [ActiveIssue] mask to MacCatalyst would mute the test — not allowed here.
• Making the Darwin socket path raise on write-to-closed is a product/behavioral change well outside small-fix bounds.

Whether MacCatalyst should simply inherit the existing OSX skip (all Darwin) is a maintainer judgement, so I am handing off rather than editing the skip.

Evidence

• Failing build: 1494308; first occurrence build 1492684 (2026-07-03); also follow-up 1494829.
• Test: src/libraries/System.Net.HttpListener/tests/HttpResponseStreamTests.cs:449.
• Behavioral tracker (async sibling): Tracking issue for test failures in .NET Apple mobile apps on NativeAOT #126697.
• These NativeAOT library tests on Apple mobile were newly enabled by [mobile] Enable NativeAOT library tests on Apple mobile platforms #125437.

Suggested reviewers / area contacts

• Newly enabled on Apple NativeAOT by [mobile] Enable NativeAOT library tests on Apple mobile platforms #125437 — @kotlarmilos for routing.
• Area owners (area-System.Net): @dotnet/ncl.

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