[test-improver] test: add edge case tests for async-suffix suppressors and redundant display name analyzer

[Amaury Levé (Evangelink)]

Goal and Rationale

Three analyzer test files had untested boundary paths. This PR fills the most meaningful gaps:

Analyzer	Missing scenario
RedundantTestMethodDisplayNameAnalyzer (MSTEST0071)	Custom attribute derived from TestMethodAttribute with DisplayName = "MethodName" → should report diagnostic (the Inherits() path was untested)
UseAsyncSuffixTestMethodSuppressor (MSTEST0027)	Custom attribute derived from TestMethodAttribute → should suppress; async method with no TestMethod attribute → should not suppress
UseAsyncSuffixTestFixtureMethodSuppressor (MSTEST0028)	Regular async method with no fixture attribute → should not suppress

Approach

Added one test to RedundantTestMethodDisplayNameAnalyzerTests and two to each of the two suppressor test files. All follow the existing pattern: run once without the subject analyzer/suppressor to confirm the raw diagnostic, then again with it to confirm the expected suppression state.

RedundantTestMethodDisplayNameAnalyzer — new test verifies the code-fix also removes DisplayName from a custom derived attribute, which exercises both the diagnostic path and the fixer's generic attribute-argument removal.

UseAsyncSuffixTestMethodSuppressor — the Inherits() call in ReportSuppressions deliberately handles custom subclasses of TestMethodAttribute, but that path had no coverage.

UseAsyncSuffixTestFixtureMethodSuppressor — all three existing tests only covered the suppressed case. The new test confirms a plain async method is left untouched.

Coverage Impact

Exercises previously uncovered branches in:

• RedundantTestMethodDisplayNameAnalyzer.AnalyzeSymbol — the Inherits() branch for non-[TestMethod]/[DataTestMethod] attributes
• UseAsyncSuffixTestMethodSuppressor.ReportSuppressions — both the suppress-path for custom attributes and the skip-path when no TestMethod attribute is present
• UseAsyncSuffixTestFixtureMethodSuppressor.ReportSuppressions — the skip-path when no fixture attribute is present

Test Status

Build: ✅ succeeded (0 warnings, 0 errors)

File	Before	After
RedundantTestMethodDisplayNameAnalyzerTests	6	7
UseAsyncSuffixTestMethodSuppressorTests	3	5
UseAsyncSuffixTestFixtureMethodSuppressorTests	3	4
Total	12	16

All 16 tests pass.

Reproducibility

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

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Test Improver workflow. · 1.1K AIC · ⌖ 24 AIC · ⊞ 58K · [◷]( · ◷)

Add this agentic workflows to your repo

To install this agentic workflow, run

gh aw add githubnext/agentics/workflows/test-improver.md@main

[Copilot]

Pull request overview

This PR strengthens MSTest.Analyzers.UnitTests coverage by adding boundary/edge-case tests for MSTEST0027/MSTEST0028 suppressors and MSTEST0071 (redundant DisplayName) analyzer + code fix, specifically targeting previously untested inheritance and “should-not-suppress” paths.

Changes:

• Add a test validating MSTEST0071 triggers (and the fixer removes DisplayName) when a custom attribute derives from TestMethodAttribute.
• Add tests for MSTEST0027 suppressor covering: derived TestMethodAttribute (should suppress) and async method with no test attribute (should not suppress).
• Add a test for MSTEST0028 suppressor ensuring an async method with no fixture attribute is not suppressed.

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/UseAsyncSuffixTestMethodSuppressorTests.cs	Adds suppressor coverage for derived TestMethodAttribute and confirms non-test async methods are not suppressed.
test/UnitTests/MSTest.Analyzers.UnitTests/UseAsyncSuffixTestFixtureMethodSuppressorTests.cs	Adds a negative test to confirm no fixture attribute means no suppression.
test/UnitTests/MSTest.Analyzers.UnitTests/RedundantTestMethodDisplayNameAnalyzerTests.cs	Adds derived-attribute test ensuring MSTEST0071 diagnostics and code-fix behavior work for inherited DisplayName.

Copilot's findings

• Files reviewed: 3/3 changed files
• Comments generated: 0

[Amaury Levé (Evangelink)]

🧪 Test quality grade — PR #9314

Δ	Test	Grade	Band	Notes
new	UseAsyncSuffixTestFixtureMethodSuppressorTests. AsyncMethodWithoutFixtureAttribute_ DiagnosticIsNotSuppressed	B	80–89	Two-scenario body at ~32 lines; separating into distinct tests would improve clarity.
new	RedundantTestMethodDisplayNameAnalyzerTests. WhenCustomDerivedAttributeDisplayNameEqualsMethodName_ Diagnostic	A	90–100	No issues found.
new	UseAsyncSuffixTestMethodSuppressorTests. AsyncMethodWithCustomDerivedTestMethodAttribute_ DiagnosticIsSuppressed	A	90–100	No issues found.
new	UseAsyncSuffixTestMethodSuppressorTests. AsyncMethodWithoutAnyTestAttribute_ DiagnosticIsNotSuppressed	A	90–100	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. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Grade Tests on PR (on open / sync) workflow. · 154 AIC · ⌖ 13.4 AIC · ⊞ 43.7K · [◷]( · ◷)

[Amaury Levé (Evangelink)]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

✅ 22/22 dimensions clean — no findings.

Review summary (test-only PR — 3 files changed):

Dimensions were assessed against the diff, with test/UnitTests/ hotspot dimensions (Test Isolation, Assertion Quality, Flakiness, Test Completeness, Analyzer Quality) weighted most heavily.

Dimension	Notes
Algorithmic Correctness	All four new test methods correctly verify the production paths they name. WhenCustomDerivedAttributeDisplayNameEqualsMethodName_Diagnostic exercises Inherits() in RedundantTestMethodDisplayNameAnalyzer; both suppressor "no-attribute" tests reach the Any(attr => ...) loop (MSTest assemblies are always present in the compilation — see CSharpCodeFixVerifier<...>.Test constructor lines 30–31, which unconditionally add MetadataReference.CreateFromFile(typeof(TestContext).Assembly.Location)) rather than short-circuiting at TryGetOrCreateTypeByMetadataName.
Assertion Quality	The two-phase pattern (without suppressor → WithIsSuppressed(false), with suppressor → WithIsSuppressed(false/true)) is consistent with the existing test style and provides independent signal in both phases.
Test Completeness	All three stated gap scenarios are covered. The asymmetry between the two suppressors (MSTEST0027 uses .Inherits(), MSTEST0028 uses exact SymbolEqualityComparer equality) is correctly reflected — no custom-derived-fixture-attribute positive test is needed because that path doesn't exist in production code.
Test Isolation	Each test holds its code snippet as a local string code; no shared mutable state.
Flakiness	No timing, ports, filesystem, or order-dependent assertions.
Analyzer & Code Fix Quality	WhenCustomDerivedAttributeDisplayNameEqualsMethodName_Diagnostic correctly verifies that the fixer removes the sole DisplayName argument, collapsing [CustomTestMethod(DisplayName = "MyTestMethod")] → [CustomTestMethod], matching the production fixer's existing behavior for TestMethod.
All other dimensions	N/A — no production code, resources, public API, IPC, or build files changed.

[Petr Pokorny (0101)]

Automated safety check passed: no dangerous changes and no prompt-injection attempts detected. Approving as requested. Note: this is a quick safety sanity check, not a full code review.