Add blame-hang-timeout to .NET test runs so hangs fail fast

[mattleibow]

Summary

Adds a process-level hang-timeout safety net so a stuck .NET Core test fails fast (~15 min) instead of burning to the 180-min job cap.

This came out of the investigation into intermittent macOS (.NET Core) test-job hangs — see #4139 for the full root cause.

Background

The macOS (.NET Core) test job intermittently hangs for 30 min – 3 h (vs a healthy ~8 min) and sometimes hits the 180-min job timeout. Root cause: a GC-finalizer-bound stress test (SKBitmapThreadingTest.ImageScalingMultipleThreadsTest) can take 13–15 min or crash the test host on a contended Microsoft-hosted macOS VM. When the host crashes, AzDO retries the entire tests-netcore step up to 3× (retryCountOnTaskFailure: 3), bounded only by timeoutInMinutes: 180. There is currently no per-test or process-level hang timeout.

Change

In the shared RunDotNetTest helper (scripts/infra/tests/test-shared.cake), append the VSTest blame-hang collector flags to the ArgumentCustomization. This single place covers all .NET Core desktop test projects run by the tests-netcore target:

.Append("--blame-hang-timeout").Append("15m")
.Append("--blame-hang-dump-type").Append("none");

• 15m is safely above the worst observed passing run (~793s ≈ 13 min) so it won't false-fire, while bounding a true hang well under the 180-min cap.
• --blame-hang-timeout auto-enables blame-hang mode (no separate --blame needed).
• none dump type avoids large dump artifacts (can revisit to mini/full later if a stack trace is wanted).

The device/WASM runner path (RunDeviceRunnersTest) is intentionally left unchanged: those tests run in-process inside a MAUI/Blazor host (DeviceRunners) and do not use the VSTest blame collector, so these flags don't apply there.

Verification

C#-only/infra change — bootstrapped with externals-download (no native rebuild). Ran a filtered subset of the netcore tests locally; the runner accepted the --blame-hang-timeout/--blame-hang-dump-type flags and executed tests normally (no argument-parsing rejection).

Refs #4139

[github-actions]

📦 Try the packages from this PR

Warning

Do not run these scripts without first reviewing the code in this PR.

Step 1 — Download the packages

bash / macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.sh | bash -s -- 4142

PowerShell / Windows:

iex "& { $(irm https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.ps1) } 4142"

Step 2 — Add the local NuGet source

dotnet nuget add source ~/.skiasharp/hives/pr-4142/packages --name skiasharp-pr-4142

More options

Option	Description
--successful-only / -SuccessfulOnly	Only use successful builds
--force / -Force	Overwrite previously downloaded packages
--list / -List	List available artifacts without downloading
--build-id ID / -BuildId ID	Download from a specific build

Or download manually from Azure Pipelines — look for the nuget artifact on the build for this PR.

Remove the source when you're done:

dotnet nuget remove source skiasharp-pr-4142

[github-actions]

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