[test-improver] test: add edge case tests for PublicTypeShouldBeTestClassAnalyzer (MSTEST0004)

[Evangelink]

🤖 Test Improver — automated AI assistant focused on improving tests for this repository.

Goal and Rationale

PublicTypeShouldBeTestClassAnalyzer (MSTEST0004) had 8 tests covering the basic "public class without [TestClass]" path and several well-known no-diagnostic cases (abstract, static, non-public, etc.), but missed four real-world scenarios:

1. public record (record class) — records have TypeKind.Class in Roslyn; the analyzer should flag them just like plain classes, but there was no test confirming this.
2. public record struct — value-type records have TypeKind.Struct; the analyzer explicitly skips non-Class types, so these should never be flagged.
3. Nested public class inside an internal outer class — GetResultantVisibility() returns Internal here, so the rule does not apply. Without a test, a future change to the visibility check could silently start flagging these.
4. Nested public class inside a public outer class — both the outer and inner classes lack [TestClass] and have resultant-public visibility, so the analyzer should flag both. Verifies that the rule walks all named types, not just top-level ones.
5. Nested public class inside a [TestClass] — the outer class is fine; the inner class has no [TestClass] and should be flagged. The fix correctly adds [TestClass] only to the inner class.

Approach

• Added 5 new [TestMethod] test cases to PublicTypeShouldBeTestClassAnalyzerTests.
• Each test uses VerifyCS.VerifyCodeFixAsync (following the existing pattern) to assert both the diagnostic location and the code-fix output.
• No production code changes.

Test Status

Test run summary: Passed!
  total: 13
  failed: 0
  succeeded: 13
  skipped: 0
  duration: 6s 633ms

✅ All 13 tests pass (MSTest.Analyzers.UnitTests, net8.0, Debug — 8 original + 5 new).

Reproducibility

./build.sh --restore   # first run only
.dotnet/dotnet test test/UnitTests/MSTest.Analyzers.UnitTests/MSTest.Analyzers.UnitTests.csproj \
  -f net8.0 --no-build -c Debug \
  --filter "ClassName=MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests"

Trade-offs

• Tests only exercise existing code paths in the analyzer — no production changes, no maintenance burden beyond the tests themselves.
• The nested-class scenarios document subtleties of GetResultantVisibility() that would otherwise be implicit and easy to break in a refactor.

Generated by Test Improver · sonnet46 6.2M · ◷

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[Copilot]

Pull request overview

This PR extends the MSTest analyzer unit test suite for MSTEST0004 (PublicTypeShouldBeTestClassAnalyzer) by adding coverage for several real-world type-shape and visibility edge cases (records and nested types), without changing production analyzer/code-fix logic.

Changes:

• Added a diagnostic + code-fix test for public record types (record classes).
• Added a no-diagnostic test for public record struct (value-type records are not TypeKind.Class).
• Added nested-type scenarios validating behavior with resultant visibility (nested public inside internal outer) and ensuring both outer/inner types are handled (including nested inside an existing [TestClass]).

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/PublicTypeShouldBeTestClassAnalyzerTests.cs	Adds 5 new MSTEST0004 unit tests covering record/record-struct and nested-type visibility/code-fix scenarios.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 0

[Evangelink]

🧪 Test quality grade — PR #8941

5 new test methods graded across 1 file (PublicTypeShouldBeTestClassAnalyzerTests.cs). All tests use the VerifyCS.VerifyCodeFixAsync Roslyn-testing pattern, which asserts both diagnostic locations (via [|...|] markers) and exact code-fix transforms — a rich assertion that covers the full analyzer contract. Every test is focused on a single scenario with a clear explanatory comment. No issues identified.

Test	Grade	Band	Notes
MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests.WhenPublicClassNestedInsideInternalClass_NoDiagnostic (new)	A	90–100	No issues found.
MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests.WhenPublicClassNestedInsidePublicNonTestClass_Diagnostic (new)	A	90–100	Asserts two diagnostic locations and exact code-fix transform for both outer and inner class.
MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests.WhenPublicClassNestedInsideTestClass_Diagnostic (new)	A	90–100	Precisely marks only the un-annotated inner class; verifies the outer [TestClass] is left untouched.
MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests.WhenPublicRecordClass_Diagnostic (new)	A	90–100	Clear AAA; asserts diagnostic location and exact code-fix transform for record class.
MSTest.Analyzers.UnitTests.PublicTypeShouldBeTestClassAnalyzerTests.WhenPublicRecordStruct_NoDiagnostic (new)	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.}

Generated by Grade Tests on PR (on open / sync) for issue #8941 · sonnet46 1.3M · ◷