test: MSTEST0061 — add edge case tests for OSPlatform.Create and mobile OS platforms

[Amaury Levé (Evangelink)]

Summary

Adds four tests covering previously untested code paths in UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzer (MSTEST0061).

The analyzer has two distinct code paths for extracting the OS platform name from RuntimeInformation.IsOSPlatform() calls:

• Property reference path: OSPlatform.Windows, OSPlatform.Linux, etc. — already tested
• OSPlatform.Create() path: OSPlatform.Create("Windows") — not previously tested

Additionally, OperatingSystem.Is*() methods for mobile/embedded platforms (iOS, Android) were not tested. These map to platform names that have no corresponding OperatingSystems enum value, so the analyzer fires but the fixer cannot produce a code fix.

Tests added

Test	Code Path	Fix?
WhenOSPlatformCreateWithKnownPlatform_Diagnostic	OSPlatform.Create("Windows") → TryGetOSPlatformFromIsOSPlatformCall Create branch	✅ fixes to [OSCondition(OperatingSystems.Windows)]
WhenOSPlatformCreateWithUnknownPlatform_Diagnostic	OSPlatform.Create("CustomOS") → Create branch, no OperatingSystems mapping	❌ analyzer fires, fixer does nothing
WhenOperatingSystemIsIOS_Diagnostic	OperatingSystem.IsIOS() → maps to "iOS", no OperatingSystems.iOS	❌ analyzer fires, fixer does nothing
WhenOperatingSystemIsAndroid_Diagnostic	OperatingSystem.IsAndroid() → maps to "Android", no OperatingSystems.Android	❌ analyzer fires, fixer does nothing

The unknown-platform and mobile-platform tests confirm that the fixer silently does nothing for unsupported platforms — a known limitation documented in the issue.

Test status

All 27 tests in UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests pass locally:

Test run summary: Passed!
total: 27, failed: 0, succeeded: 27, skipped: 0

Fixes#9808

[Copilot]

Pull request overview

Adds MSTEST0061 edge-case coverage for OSPlatform.Create and unsupported mobile platforms.

Changes:

• Tests known and custom OSPlatform.Create values.
• Tests iOS and Android diagnostics.
• Validates the supported Windows code fix.

Show a summary per file

File	Description
UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests.cs	Adds four analyzer and fixer edge-case tests.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 3
• Review effort level: Medium

[github-actions]

Note

🤖 Automated review by GitHub Copilot. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

Review Summary

All 22 dimensions reviewed — no findings.

Dimension	Verdict
1. Algorithmic Correctness	✅ N/A — test-only change
2. Error Handling	✅ N/A
3. Concurrency / Thread Safety	✅ N/A
4. Performance	✅ N/A
5. Security	✅ N/A
6. Public API Surface	✅ N/A — no public API changes
7. Backward Compatibility	✅ N/A
8. Cross-TFM Correctness	✅ N/A
9. Localization	✅ N/A
10. Naming & Conventions	✅ Clean — test names follow existing patterns
11. Code Style	✅ Clean — consistent with adjacent tests
12. Documentation / Comments	✅ Clean — each test has a clear comment explaining the code path exercised
13. Test Quality	✅ Clean — tests cover distinct code paths (Create branch, unknown platform, mobile OS methods)
14. Test Assertion Conventions	✅ Clean — uses VerifyCS.VerifyCodeFixAsync / VerifyAnalyzerAsync per project conventions
15. Scope Discipline	✅ Clean — single concern (edge-case test coverage)
16. Duplication	✅ Clean — no unnecessary repetition beyond the structural boilerplate inherent to Roslyn verifier tests
17. Disposal & Lifetime	✅ N/A
18. Configuration	✅ N/A
19. Logging & Diagnostics	✅ N/A
20. IPC / Wire Compat	✅ N/A
21. Build Infrastructure	✅ N/A
22. TODO Policy	✅ N/A — no TODOs

Verdict: All clear. Four well-targeted tests covering previously untested analyzer branches. No issues found.

[Copilot]

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0 new
• Review effort level: Medium

[github-actions]

🧪 Test quality grade — PR #9818

Grade	Test	Notes
A (90–100)	new UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests. WhenOSPlatformCreateWithKnownPlatform_ Diagnostic	Clear AAA; VerifyCodeFixAsync asserts both diagnostic detection and the fix transformation. No issues found.
A (90–100)	new UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests. WhenOSPlatformCreateWithUnknownPlatform_ Diagnostic	Clear AAA; VerifyCodeFixAsync(code, code) correctly verifies the fixer is a no-op for unmapped platforms. No issues found.
A (90–100)	new UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests. WhenOperatingSystemIsIOS_ Diagnostic	Clear AAA; VerifyCodeFixAsync(code, code) correctly verifies the fixer is a no-op for iOS. No issues found.
A (90–100)	new UseOSConditionAttributeInsteadOfRuntimeCheckAnalyzerTests. WhenOperatingSystemIsAndroid_ Diagnostic	Clear AAA; VerifyCodeFixAsync(code, code) correctly verifies the fixer is a no-op for Android. No issues found.

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Re-run with
/grade-tests.}

🤖 Automated content by GitHub Copilot. Generated by the Grade Tests on PR (on open / sync) workflow. · 31.6 AIC · ⌖ 6.43 AIC · ⊞ 9.5K · [◷]( · ◷)