Fix MSTEST0063 to detect invalid constructors on derived TestClass attributes

[Amaury Levé (Evangelink)]

Fixes#9836

Problem

TestClassConstructorShouldBeValidAnalyzer (MSTEST0063) validates that [TestClass]-decorated classes have a public parameterless constructor or a public TestContext-parameter constructor.

The guard in AnalyzeSymbol used an exact-match check (SymbolEqualityComparer.Default.Equals) against TestClassAttribute, so classes decorated with derived test-class attributes — including the built-in [STATestClass] and any custom class MyAttr : TestClassAttribute — were silently skipped. Because MSTest discovers such classes at runtime via Inherits() logic, a private/internal constructor causes a runtime instantiation failure with no analyzer warning.

Fix

Replace the exact-match guard with the shared IsTestClass() helper, which calls Inherits() and matches the runtime discovery behavior:

// Before!namedTypeSymbol.GetAttributes().Any(attr =>SymbolEqualityComparer.Default.Equals(attr.AttributeClass,testClassAttributeSymbol))// After!namedTypeSymbol.IsTestClass(testClassAttributeSymbol)

Tests

Four new tests added to TestClassConstructorShouldBeValidAnalyzerTests.cs:

Scenario	Expected
[STATestClass] + private constructor	Diagnostic
[STATestClass] + public parameterless constructor	NoDiagnostic
Custom derived TestClass attr + internal constructor	Diagnostic
Custom derived TestClass attr + public constructor	NoDiagnostic

Trade-offs

This is a behavior change: previously, classes with derived [TestClass] attributes and invalid constructors produced no warning; after this fix they do. This is the correct behavior — the fix brings the analyzer in line with MSTest's runtime class-discovery logic.

Build and MSTest.Analyzers.UnitTests (net472 + net8.0) pass locally.

[Copilot]

Pull request overview

Updates MSTEST0063 to validate constructors on classes using derived TestClassAttribute types.

Changes:

• Uses the shared inheritance-aware IsTestClass() helper.
• Adds coverage for built-in and custom derived attributes.

Show a summary per file

File	Description
TestClassConstructorShouldBeValidAnalyzer.cs	Enables derived test-class attribute detection.
TestClassConstructorShouldBeValidAnalyzerTests.cs	Tests valid and invalid constructor scenarios.

Review details

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

[github-actions]

Clean fix. The IsTestClass helper (via Inherits) correctly walks the attribute type hierarchy, which is exactly what was missing with the old SymbolEqualityComparer.Default.Equals exact-match check. This is consistent with how other analyzers (TestClassShouldHaveTestMethodAnalyzer, PublicMethodShouldBeTestMethodAnalyzer, etc.) already guard their IsTestClass checks.

Tests cover both [STATestClass] (built-in derived) and a custom derived attribute, with positive and negative cases. No issues found.

[github-actions]

🧪 Test quality grade — PR #9851

Grade	Test	Notes
A (90–100)	new TestClassConstructorShouldBeValidAnalyzerTests. WhenDerivedTestClassAttributeHasPrivateConstructor_ Diagnostic	Clear AAA; asserts exact diagnostic location and arguments via VerifyCodeFixAsync. No issues found.
A (90–100)	new TestClassConstructorShouldBeValidAnalyzerTests. WhenDerivedTestClassAttributeHasPublicParameterlessConstructor_ NoDiagnostic	Clean negative-path test; VerifyCodeFixAsync(code, code) meaningfully asserts no diagnostic is produced. No issues found.
A (90–100)	new TestClassConstructorShouldBeValidAnalyzerTests. WhenCustomDerivedTestClassAttributeHasInternalConstructor_ Diagnostic	Clear AAA; custom-attribute inheritance chain is exercised with exact diagnostic location and arguments. No issues found.
A (90–100)	new TestClassConstructorShouldBeValidAnalyzerTests. WhenCustomDerivedTestClassAttributeHasPublicConstructor_ NoDiagnostic	Clean negative-path test; mirrors the diagnostic counterpart symmetrically, exercising the full custom-attribute path. 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. · 32.6 AIC · ⌖ 6.32 AIC · ⊞ 9.5K · [◷]( · ◷)

[github-actions]

🔴 Build Failure Analysis

Build: FAILED (236.6s) · 5 errors · 1 warning

Root Cause

All 4 compilation errors are the same issue — analyzer rule CA1416 (platform compatibility) on two call sites in FileLoggerTests.cs:

Line	Class	Issue
465	LoopTrackingTask	Calls ITask.RunLongRunning() which is marked [UnsupportedOSPlatform("browser")]
490	NeverCompletingTask	Same

(Each error is reported twice — once per TFM.)

The interface method ITask.RunLongRunning was annotated with [UnsupportedOSPlatform("browser")] and [UnsupportedOSPlatform("wasi")], but the two test helper classes that delegate to it don't suppress the warning.

Suggested Fix

Add [UnsupportedOSPlatform("browser")] to lines 464 and 489, or (simpler for test code) add a #pragma warning disable CA1416 / #pragma warning restore CA1416 around each call site. See inline suggestions below.

🤖 Automated content by GitHub Copilot. Generated by the Build Failure Analysis workflow. · 45.4 AIC · ⌖ 5.79 AIC · ⊞ 7.3K · [◷]( · ◷)

[github-actions]

🤖 Automated content by GitHub Copilot. Generated by the Build Failure Analysis workflow. · 45.4 AIC · ⌖ 5.79 AIC · ⊞ 7.3K · ◷

[Amaury Levé (Evangelink)]

The CA1416 build failure is a pre-existing issue in test/UnitTests/Microsoft.Testing.Platform.UnitTests/Logging/FileLoggerTests.cs (the LoopTrackingTask / NeverCompletingTaskITask helpers), which this PR does not touch. It stems from the [UnsupportedOSPlatform("browser")] annotation on ITask.RunLongRunning and is unrelated to the MSTEST0063 analyzer change.

It's being handled separately (branch dev/amauryleve/fix-ca1416-filelogger-tests), so I'm keeping this PR surgical and not pulling the unrelated test fix in here. This PR will go green once that fix lands on main and this branch is rebased.

[Amaury Levé (Evangelink)]

/backport to rel/4.3

[github-actions]

Started backporting to rel/4.3: https://github.com/microsoft/testfx/actions/runs/29831582249