[thomhurst]

Description

Fixes the flaky tests and broken CI jobs that failed PRs for reasons unrelated to their diffs. I swept every failed run from 2026-09-19 to 2026-10-17 (failed jobs, failed steps and failed test names; no run in the last two weeks needed a rerun to pass). Each fix removes the root cause. Nothing is retried, skipped, or given a bigger timeout.

Flakes fixed

1. ParallelMapTests.SelectorException_StopsSiblingsPullingNewItems (TUnit.UnitTests)

• Evidence (8 failures, 8 unrelated branches, all three OSes): Expected to be less than 10000 but received 10000. Runs 39040849980 (PR fix(engine): report the engine mode actually selected in the banner #7085), 38845922577, 38784313529, 38476335584, 38420421501, 38259927032, 37028768311, 35479372550.
• Root cause (timing assumption in the test): The test let 10,000 Task.Yield items race the faulting worker. If that worker was preempted between the fault and Volatile.Write(ref cursor, count), the sibling workers processed every item. Parking the cursor is best-effort by design, so this is not a product bug.
• Fix: Each of 4 workers takes one item and suspends on it. Item 0 is a ValueTask backed by an IValueTaskSource that reports when the worker awaits it and runs the continuation inline when faulted, so the worker's catch has parked the cursor before the test releases the siblings. The test now asserts exactly invoked == 4.
• Proof: Before: 1 failure in 903 parallel runs ([Repeat(300)] x3). After: 0 failures in 3,010. Mutation check: with the cursor park removed, 301 of 301 fail.

2. PerTestWebApplicationTestDisposalFailureTests.DisposeFactoryAsync_Disposes_Remaining_Factories_When_One_Throws (TUnit.AspNetCore.Tests)

• Evidence (7 failures, Windows and Ubuntu, unrelated renovate/fix branches): Expected exception message to contain "Stop failed on purpose." but no exception was thrown. Runs 38845905433, 38784313529 (x2), 38578738515, 38548172361, 38469227227, 38428778438.
• Root cause (race in the test): This is the double stop from [Bug]: [Test Failure] After(Test) hook failed: The CancellationTokenSource has been disposed. #6339. A minimal-hosting SUT's app.Run() wakes on ApplicationStopping and calls Host.StopAsync concurrently with WebApplicationFactory.DisposeAsync. This test turns off the stop-once wrapper (SuppressHostedServiceExecutionContextFlow => false), and its hosted service failed only on stop call Repeat attributes  #1. When app.Run() made that call, the dispose path saw a clean second stop. The default product path, with the wrapper on, already makes both callers see the same result, so this is not a product bug.
• Fix: The service fails every stop until the test calls StopFailing() in a finally, so the stop on the dispose path always fails and the session-end re-disposal still succeeds.
• Proof: Before: 12 failures in 303 runs ([Repeat(100)] x3). After: 0 failures in 505, and every session passed, including the session-end re-disposal.

3. HtmlReporterTests.BuildReportData_Ignores_Default_Start_Timestamps (TUnit.Engine.Tests)

• Evidence (1 failure, Windows): 0.0013d should be within 1d of 250d but was not. Run 38548146421.
• Root cause (shared process-wide state): ConsumeAsync starts an ActivityCollector, which listens to every activity in the process. Stopping_Activity_Collection_Preserves_Spans_For_Report_Data runs in parallel and emits a test session span of about 1 µs. When that span stopped while the other test's collector was live, BuildReportData used it as the run duration.
• Fix: Both tests share a [NotInParallel] key, and the timestamp test now disposes its reporter.
• Proof: The race window is microseconds wide and didn't occur naturally in 10k+ local runs. Emitting a session span between ConsumeAsync and BuildReportData reproduces the exact CI signature (0.0033d should be within 1d of 250d), and a probe showed parallel repeats collecting each other's spans (spans=4).

4. OtlpReceiverIngestionTests.Receiver_Forwarding_PropagatesHeadersAndCountsSuccess (TUnit.OpenTelemetry.Tests)

• Evidence (1 failure, Ubuntu): HttpListenerException: Failed to listen on prefix 'http://127.0.0.1:34573/' because it conflicts with an existing registration. Run 38418242800.
• Root cause (port race in the test): The test called FindFreePort() and bound the port later, so another listener could take it in between. The product's LoopbackHttpListenerFactory.Create() already retries exactly this case; this test and Receiver_DrainAsync_WaitsForInFlightForwardBeforeReturning didn't use it.
• Fix: Both tests now use LoopbackHttpListenerFactory.Create().

5. PerTestServerStartupTests "Server startup time is recorded accurately" (examples/TUnit.Example.Asp.Net.TestProject)

• Evidence (1 failure, Ubuntu): Expected to be greater than or equal to 10/14/2026 23:25:33 ... but received 10/14/2026 23:25:33. Run 38652565258.
• Root cause (wrong assumption in the test): WebApplicationTest builds the factory, which starts the server, in its Before(Test) hook, before the test body runs. The test took its "before" timestamp in the body and passed only while hook-to-body latency stayed under a 500 ms margin. Locally the server always started before the body (lead 0 to 27 ms over 201 runs); a loaded runner exceeded 500 ms.
• Fix: Startup is now bounded by SetupCalledAt, which SetupAsync records before the factory is built, and by the moment CreateClient returns. The 500 ms margins are gone.

CI job fixed

6. iOS / tvOS / MacCatalyst smoke test: "Build the smoke test"

• Evidence: Failed on every PR since 2026-10-13 (about 90 runs each), e.g. run 39040681946 (PR fix: skip tests marked with an empty skip reason #7083): This version of .NET for tvOS (27.0.12212-net11-rc.2) requires Xcode 27.0. The current version of Xcode is 26.6.
• Root cause (environment, deterministic): chore(deps): update dependency dotnet-sdk to v11.0.100-rc.2.26504.105 #7054 moved to SDK 11.0.100-rc.2, whose workload set installs the 27.x Apple SDK packs. Those need Xcode 27, and macos-26 has only Xcode 26.x.
• Fix: These three jobs now run on the xcode-27 runner image (Xcode 27.0 default, public preview) with its iOS 27.0 (iPhone 17) and tvOS 27.0 (Apple TV 4K (3rd generation)) simulators. These jobs can't run locally, so this PR's own smoke run is the proof.

Investigated, not fixed

Failure	Evidence	Disposition
KeyedNotInParallelCrossPhaseTests.UnconstrainedTest_RunsAlongsideKeyedNotInParallelTest (macOS, 32 s)	38445846836	Left alone: it's in the ConstraintKeyScheduler area that PRs #7084 and #7087 are changing.
Test2_KeyedSerializes(1/2)	4 runs, last on 2026-09-28	Same scheduler area; no failures since 2026-09-28.
RpcTests net8.0: all tests fail after "Underlying process was forcefully terminated"	38534227194 (macOS)	1 occurrence in 4 weeks; the child process hung or was killed on a slow runner. Not enough evidence for a root cause.
CloudShop integration-tests: Aspire app didn't start within 300 s	38638434987	1 occurrence, on an ASP.NET Core bump PR; not clearly unrelated.
InstallPlaywrightModule: Could not get lock /var/lib/dpkg/lock-frontend	38445865182	External: another apt-get on the runner held the lock. The module already retries twice.
lychee link check: 503 from github.com	38415245139	External, 1 occurrence.
dotnet workload install failures on all six smoke platforms	11 runs on 2026-10-13/14, e.g. 38461271154	External: workload set 11.0.100-rc.2.26509.2 referenced microsoft.net.sdk.android 37.2.0-rc.2.84 before it was on nuget.org. It resolved on its own.
Restore NU1902 MessagePack 2.5.302 advisory	e.g. 39038409448	New advisory treated as an error; already fixed on main by #7072.
ExpectedStateTests.Pass, Without_STA, *_Library_Has_No_API_Changes, Waiting_Continuations_Do_Not_Run_On_The_Initializing_Thread, IndexOutOfRangeException in Activity.Stop()	2026-09-19 to 2026-09-29	Already fixed (#6857, #6898, #6906, #6933); no failures since.
AutoConfigureOpenTelemetryOptOutTests (known Ubuntu flake)	none in the window	Didn't recur.
Build / Locale-build / "Compile documentation snippets" failures	renovate analyzer, EF and Extensions branches; oss-scanner branch	Caused by those PRs.

Tests run

• TUnit.UnitTests ParallelMapTests/*: net10.0 and net8.0, 13/13 each; the changed test passed 3,010/3,010 under [Repeat(300)].
• TUnit.AspNetCore.Tests: full project (net10.0), 125/125; the changed test passed 505/505 under [Repeat(100)].
• TUnit.OpenTelemetry.Tests: full project (net10.0), 42/42; OtlpReceiverIngestionTests/* 5x, 55/55.
• TUnit.Engine.Tests HtmlReporterTests/* (net10.0): 44/44, 6x.
• TUnit.Example.Asp.Net.TestProject PerTestServerStartupTests/* (net10.0): 5/5; the changed test passed 201/201 under [Repeat(200)].

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Checklist

• I have written tests that prove my fix is effective or my feature works

Summary by CodeRabbit

• Tests
  • Improved coverage for server startup timing, service disposal failures, parallel execution, and HTML reporting.
  • Made parallel-execution checks more controlled and repeatable.
  • Improved setup of loopback listeners in forwarding tests.
• Chores
  • Updated iOS, tvOS, and Mac Catalyst smoke-test environments to Xcode 27 and newer simulator runtimes.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-17T15:43:09.009969Z	14f9f72	PR opened

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📝 Walkthrough

The pull request updates Apple platform smoke-test settings and changes tests for startup timing, factory disposal, HTML reporting, OTLP listener setup, and parallel map worker coordination.

Changes: Apple Platform Smoke Tests

Layer / File(s)	Summary
Xcode 27 smoke configuration .github/workflows/platform-smoke.yml	The iOS, tvOS, and MacCatalyst jobs use Xcode 27. The workflow updates the iOS and tvOS simulator runtimes and selects an Apple TV 4K (3rd generation) device. It also selects /Applications/Xcode_27.0.app.

ASP.NET Core Test Updates

Layer / File(s)	Summary
Startup and disposal test assertions examples/TUnit.Example.Asp.Net.TestProject/PerTestServerStartupTests.cs, tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs	The startup test checks recorded timestamps against setup and client creation. The factory disposal test uses a retained service instance that throws on every stop until the test disables failures.

HTML Reporter Test Serialization

Layer / File(s)	Summary
Session-span test coordination tests/TUnit.Engine.Tests/HtmlReporterTests.cs	A shared SessionSpanKey serializes the activity-collection and default-timestamp tests against tests that use the same key.

OTLP Receiver Listener Tests

Layer / File(s)	Summary
Loopback listener setup tests/TUnit.OpenTelemetry.Tests/OtlpReceiverIngestionTests.cs	The forwarding and drain tests use LoopbackHttpListenerFactory.Create() instead of manually probing for a free port and creating an HttpListener.

Parallel Map Test Coordination

Layer / File(s)	Summary
Controlled sibling-pull test tests/TUnit.UnitTests/ParallelMapTests.cs	The test gates four workers, faults item zero after its await is observed, and checks that only the initial worker items were invoked. A value-task source helper exposes the await observation.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: glennwatson, snakybeaky

Merge Risk: 🔵 Low · up to 14f9f

The reporter duration test may still be flaky when session-span tests overlap. Coordinate those tests or confirm their collectors are isolated; the remaining risk is low.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 20 functions across 5 files. (1 skipped: 1…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title accurately summarizes the two main changes: fixing flaky tests and repairing Apple smoke jobs. It is specific, concise, and relevant to the changeset.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 20 functions across 5 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @tests/TUnit.Engine.Tests/HtmlReporterTests.cs:
- Line 584: Add the SessionSpanKey non-parallelization attribute to the two
HtmlReporterConfigurationTests that emit SpanTestSession, or isolate their
activity collectors, so those tests cannot affect the duration test’s
TotalDurationMs.

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• Run ID: e582534a-f63f-4402-8646-ee156c2a33a5

📥 Commits

Reviewing files that changed from the base of the PR and between 3ae682a and 14f9f72.

📒 Files selected for processing: 6

• .github/workflows/platform-smoke.yml
• examples/TUnit.Example.Asp.Net.TestProject/PerTestServerStartupTests.cs
• tests/TUnit.AspNetCore.Tests/CreateFactoryAsyncTests.cs
• tests/TUnit.Engine.Tests/HtmlReporterTests.cs
• tests/TUnit.OpenTelemetry.Tests/OtlpReceiverIngestionTests.cs
• tests/TUnit.UnitTests/ParallelMapTests.cs

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[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no actionable issues were found.

Summary

This PR removes timing races from five tests and updates the Apple smoke jobs for Xcode 27.

• The parallel-map test controls when workers can take new items.
• The disposal test keeps the hosted-service failure active until its check finishes.
• The HTML reporter tests that use session spans run apart from each other.
• The OTLP forwarding tests bind their upstream listeners with port retries.
• The startup-time test measures from setup through client creation.
• Apple smoke jobs build on the Xcode 27 runner and matching simulators.

No actionable issues were found. This review checked source code; it did not run tests or Apple smoke jobs.

_{Reviews (1) · Last reviewed commit: "ci: run the Apple smoke tests on the Xco..." · Reviewed by Greptile}

[github-actions]

Review of #7095

I reviewed the diff only. I didn't build or run any of the tests.

The fixes address root causes: none of them adds retries, skips or longer timeouts.

• ParallelMapTests: Gating each worker on one item makes the ordering deterministic, and invoked == workers is a much stronger assertion than < count. ManualResetValueTaskSourceCore runs continuations inline by default. That is what lets the worker's catch park the cursor before siblingsGate is released. The comment says so, which is good.
  • One small hazard: the test relies on ParallelMap awaiting the ValueTask directly. If ParallelMap later switches to .AsTask() or ConfigureAwait with a context, the inline guarantee silently weakens and the flake could return. Consider a one-line comment saying the test depends on this.
• ThrowingOnStopService: Failing every stop until StopFailing() is called handles the concurrent double stop correctly. The try/finally makes sure session-end disposal still succeeds. This is a clean fix.
• HtmlReporterTests: Sharing a [NotInParallel] key across tests that emit or assert on the session span is the right way to handle the process-wide listener. Adding using on the reporter is a good cleanup.
• OtlpReceiverIngestionTests: Using LoopbackHttpListenerFactory.Create() removes the probe-then-bind race. The using var upstreamListenerScope = upstreamListener; pattern works but is slightly awkward. Having Create return a disposable tuple, or deconstructing straight into a using, would read better.
• PerTestServerStartupTests (example): Comparing against SetupCalledAt instead of a wall-clock ±500 ms window removes the timing dependency.
• platform-smoke.yml: I can't verify that the xcode-27 runner label, the Xcode_27.0.app path, the iOS-27-0 / tvOS-27-0 simulator names or the Apple TV 4K (3rd generation) device exist. If any is wrong, the job fails at setup or simulator start. Please confirm with a successful run of this workflow. Pinning the Xcode path in two places (runner label and xcode-select) is also brittle. A glob or xcode-select by version lookup would avoid breaking again on the next minor bump.

No blocking issues. LGTM, pending confirmation that the platform-smoke workflow runs green.