Add report file retry helper tests

[Amaury Levé (Evangelink)]

Adds deterministic unit coverage for ReportFileWriterHelper.RetryWhenIOExceptionAsync.

The tests pin immediate success, transient I/O retries, the strict timeout boundary, the final post-timeout invocation, non-I/O and cancellation propagation, exact invocation counts, and fake-clock read sequences without real-time sleeps.

Closes #10598

[Copilot]

Pull request overview

Adds deterministic unit coverage for shared report-file retry behavior.

Changes:

• Covers success, retry, timeout-boundary, exception, and cancellation paths.
• Verifies invocation counts and fake-clock reads without real delays.

Show a summary per file

File	Description
test/UnitTests/Microsoft.Testing.Extensions.UnitTests/ReportFileWriterHelperTests.cs	Adds comprehensive tests for RetryWhenIOExceptionAsync.

Review details

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• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Balanced

[github-actions]

🧵 Parallel-safety audit — PR #10635

The only change in this PR is a new test file, test/UnitTests/Microsoft.Testing.Extensions.UnitTests/ReportFileWriterHelperTests.cs, adding ReportFileWriterHelperTests for ReportFileWriterHelper.RetryWhenIOExceptionAsync.

Reviewed every test method and the private SequenceClock fixture: none touch process-global state (env vars, CWD, culture, console, static fields), the filesystem, or a [ResourceLock] / [DoNotParallelize] declaration. The clock is a fully isolated in-memory fake constructed fresh per test, and the code under test (ReportFileWriterHelper.RetryWhenIOExceptionAsync) only calls the injected IClock and the caller-supplied delegate — no shared global reads. No lifecycle members ([TestInitialize]/[ClassInitialize]/etc.) were added or changed, and no assembly-level parallelization declaration changed.

Nothing to flag for parallel-safety.

Audited Microsoft.Testing.Extensions.UnitTests at scope MethodLevel (workers: CPU count, per [assembly: Parallelize(Scope = ExecutionScope.MethodLevel, Workers = 0)] in Program.cs).

_{Re-run with /parallel-audit.}

🤖 Automated content by GitHub Copilot. Generated by the Parallel-safety audit on PR (on open / sync) workflow. · auto · 38.6 AIC · ⌖ 2.85 AIC · ⊞ 24.8K · [◷]( · ◷)