[ci-scan] Flaky: CreateTimerNonRepeatingDoesNotRepeat — NullReferenceException on macOS arm64 Helix

[github-actions]

Summary

DispatcherTests.CreateTimerNonRepeatingDoesNotRepeat fails on macOS arm64 (osx.15.arm64.maui.open) Helix with a NullReferenceException thrown inside the async timer-tick callback, breaking the maui-pr pipeline.

Build Information

• Pipeline: maui-pr (definition 302)
• Build: 1459938
• Helix job: 1459bd87-901b-4e04-a5cb-ffdf997b94f9 (osx.15.arm64.maui.open)
• Branch: main
• First seen: 2026-06-11
• Occurrences: 1 confirmed in latest build (separate macOS arm64 unit test failures also seen in build 1446345)

Affected Legs

• macOS arm64 — Windows Helix Unit Tests (Debug) job / osx.15.arm64.maui.open queue
• Microsoft.Maui.UnitTests.dll work item (ExitCode 1)

Error Message

CreateTimerNonRepeatingDoesNotRepeat [FAIL]
      System.NullReferenceException : Object reference not set to an instance of an object.
      Stack Trace:
        /_/src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs(140,0): at Microsoft.Maui.UnitTests.Dispatching.DispatcherTests.<>c.<<CreateTimerNonRepeatingDoesNotRepeat>b__10_0>d.MoveNext()
        --- End of stack trace from previous location ---
        /_/src/Core/tests/UnitTests/TestClasses/DispatcherStub.cs(148,0): at Microsoft.Maui.UnitTests.DispatcherTest.<>c__DisplayClass1_0.<<Run>b__0>d.MoveNext()
   Microsoft.Maui.UnitTests  Total: 834, Errors: 0, Failed: 1, Skipped: 3, Time: 1.840s

Recommended Action

Investigate src/Core/tests/UnitTests/Dispatching/DispatcherTests.cs and src/Core/tests/UnitTests/TestClasses/DispatcherStub.cs. The test creates a non-repeating timer and checks it ticks exactly once. The NullReferenceException originates in the async state machine inside the tick callback, suggesting either the DispatcherStub or the IDispatcherTimer implementation has a null reference in its macOS/Helix environment setup. Check if Dispatcher.GetForCurrentThread() returns null on macOS arm64 in the Helix test environment, or if the timer's internal state is null when the callback fires.

Generated by CI Failure Scanner · maui-pr build 1459938

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