[test-improver] test: add edge case tests for DoNotUseShadowingAnalyzer (MSTEST0036)

[Amaury Levé (Evangelink)]

Goal and Rationale

DoNotUseShadowingAnalyzer (MSTEST0036) had 18 tests, but three distinct code paths in the analyzer's logic were completely untested:

Untested path	Guard
Multi-level inheritance — shadowing a grandparent member through an empty intermediate class	GetBaseMembers while-loop walking all BaseType ancestors
Property with same name but different type	SymbolEqualityComparer.Default.Equals(propertySymbol.Type, basePropertySymbol.Type) guard in IsMemberShadowing
Field with same name as base field	IsMemberShadowing returns false for IFieldSymbol (only IMethodSymbol and IPropertySymbol are handled)

Approach

Added three [TestMethod] entries to DoNotUseShadowingAnalyzerTests.cs:

Test	What it covers
WhenTestClassShadowsGrandparentMemberThroughIntermediateClass_Diagnostic	[TestClass]DerivedClass : IntermediateClass : GrandparentClass where only GrandparentClass declares Method() and DerivedClass redeclares it → GetBaseMembers walks through the empty IntermediateClass to find GrandparentClass.Method, diagnostic fires
WhenTestClassHasSamePropertyNameAsBaseClassButDifferentType_NoDiagnostic	Base has int Property, derived has new string Property — types differ, SymbolEqualityComparer check returns false → no diagnostic
WhenTestClassHasSameFieldNameAsBaseClass_NoDiagnostic	Base has int Field, derived has new int Field — IsMemberShadowing has no IFieldSymbol branch → falls through to return false → no diagnostic

Coverage Impact

	Before	After
Tests in DoNotUseShadowingAnalyzerTests	18	21

Trade-offs

Purely additive — no production code changes, no new dependencies.

Test Status

All 21/21 tests pass (net8.0, Debug):

Test run summary: Passed!
total: 21
failed: 0
succeeded: 21
duration: 4s 902ms

Reproducibility

.dotnet/dotnet test test/UnitTests/MSTest.Analyzers.UnitTests/MSTest.Analyzers.UnitTests.csproj \
-f net8.0 --no-build -c Debug \
--filter "FullyQualifiedName~DoNotUseShadowingAnalyzerTests"

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Pull request overview

Adds targeted unit tests for the MSTest analyzers project to cover previously untested edge paths in DoNotUseShadowingAnalyzer (MSTEST0036), improving confidence in inheritance-walking and member-type handling behavior.

Changes:

• Add a diagnostic test for shadowing a grandparent member through an empty intermediate base type.
• Add no-diagnostic tests for (1) same property name with different type and (2) same field name as base field.

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/DoNotUseShadowingAnalyzerTests.cs	Adds 3 new analyzer tests covering grandparent-member shadowing, property type mismatch, and field hiding scenarios.

Review details

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

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9489

Δ	Test	Grade	Band	Notes
new	DoNotUseShadowingAnalyzerTests. WhenTestClassHasSameFieldNameAsBaseClass_ NoDiagnostic	A	90–100	Clear single scenario; no-diagnostic assertion is idiomatic and complete for Roslyn analyzer tests.
new	DoNotUseShadowingAnalyzerTests. WhenTestClassHasSamePropertyNameAsBaseClassButDifferentType_ NoDiagnostic	A	90–100	No issues found.
new	DoNotUseShadowingAnalyzerTests. WhenTestClassShadowsGrandparentMemberThroughIntermediateClass_ Diagnostic	A	90–100	Diagnostic location marker asserts the full inheritance chain is checked; comment explains the scenario clearly.

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

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[Amaury Levé (Evangelink)]

Note

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Review: PR #9489 — Edge case tests for DoNotUseShadowingAnalyzer (MSTEST0036)

This PR adds three test methods to cover previously untested code paths in DoNotUseShadowingAnalyzer. All three tests correctly reflect the analyzer's current behavior and are well-structured.

Dimension findings

#	Dimension	Verdict
17	Documentation Accuracy	🟡 2 MODERATE
18	Analyzer & Code Fix Quality	🟡 2 MODERATE (same findings)

✅ 20/22 dimensions clean.

• Test 2 (WhenTestClassHasSamePropertyNameAsBaseClassButDifferentType_NoDiagnostic) — The comment says "not considered shadowing", which implies intentional design, but the production code has no corresponding explanation for why different-type same-name properties are excluded from the diagnostic. If intentional, the rationale should be documented in IsMemberShadowing; if a gap, a follow-up issue should be filed.
• Test 3 (WhenTestClassHasSameFieldNameAsBaseClass_NoDiagnostic) — GetBaseMembers collects IFieldSymbol members (they pass the skip filter), but IsMemberShadowing has no IFieldSymbol branch and returns false by fallthrough — no comment in the production code explains this omission. Same ask: document the intent or track the gap.

Correctness verification

All three new tests correctly exercise the claimed code paths:

Test	Path verified	Verdict
WhenTestClassShadowsGrandparentMemberThroughIntermediateClass_Diagnostic	GetBaseMembers while-loop traverses IntermediateClass (no members), then GrandparentClass (finds Method) → diagnostic fires	✅
WhenTestClassHasSamePropertyNameAsBaseClassButDifferentType_NoDiagnostic	IsMemberShadowing property branch: SymbolEqualityComparer.Default.Equals(string, int) → false → no diagnostic	✅
WhenTestClassHasSameFieldNameAsBaseClass_NoDiagnostic	IsMemberShadowing: neither method nor property branch matches IFieldSymbol → falls through to return false → no diagnostic	✅

Minor observation (NIT)

The new test names (WhenTestClassShadows..., WhenTestClassHas...) don't follow the existing pattern in the file (WhenTestClassHave...). This is inconsistent but a very minor style nit that does not need to block the PR.

Assertion style

VerifyCS.VerifyAnalyzerAsync is the correct assertion mechanism for this project. BannedSymbols.txt bans AwesomeAssertions; no violations found.

---

The tests are functionally correct and a welcome addition to the suite. The inline comments above ask the team to clarify design intent vs. gap for the two NoDiagnostic cases — no code changes are strictly required to merge, but the clarification would improve long-term maintainability.