[test-improver] test: add edge case tests for DoNotUseSystemDescriptionAttributeAnalyzer (MSTEST0031)

[Evangelink]

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Goal and Rationale

DoNotUseSystemDescriptionAttributeAnalyzer (MSTEST0031) had 5 tests covering the main diagnostic and code-fix paths, but two real-world behaviors were undocumented:

1. [DataTestMethod] + [System.ComponentModel.Description] → diagnostic — DataTestMethodAttribute inherits from TestMethodAttribute. The analyzer detects test methods via attribute.AttributeClass.Inherits(testMethodAttributeSymbol), so [DataTestMethod] should trigger the same diagnostic as [TestMethod]. No test confirmed this inheritance path.

2. [TestMethod] + MSTest's [Description] → no diagnostic — When using Microsoft.VisualStudio.TestTools.UnitTesting is in scope (without using System.ComponentModel), the short-form [Description] resolves to Microsoft.VisualStudio.TestTools.UnitTesting.DescriptionAttribute — the correct attribute. The analyzer checks via SymbolEqualityComparer.Default.Equals(attribute.AttributeClass, systemDescriptionAttributeSymbol) (not Inherits()), so it must not fire here. This test guards against a future regression that might accidentally flag the correct usage.

Approach

Added 2 new [TestMethod] test cases to DoNotUseSystemDescriptionAttributeAnalyzerTests. No production code changes.

Test Status

Test run summary: Passed!
  total: 7
  failed: 0
  succeeded: 7
  skipped: 0
  duration: 8s 605ms

✅ All 7 tests pass (MSTest.Analyzers.UnitTests, net8.0, Debug — 5 original + 2 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.Test.DoNotUseSystemDescriptionAttributeAnalyzerTests"

Trade-offs

• Tests exercise existing code paths only — no production changes, no maintenance burden beyond the tests.
• The [DataTestMethod] test pins the Inherits() check behavior for derived test-method attributes.
• The MSTest [Description] test guards against accidentally flagging the correct usage.

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Pull request overview

This PR expands unit test coverage for the DoNotUseSystemDescriptionAttributeAnalyzer (MSTEST0031) in MSTest.Analyzers.UnitTests by adding two edge-case tests that document and lock in real-world attribute resolution/inheritance behavior.

Changes:

• Add a new diagnostic + code-fix test ensuring [DataTestMethod] (derived from TestMethodAttribute) is treated as a test method and still triggers MSTEST0031 when using System.ComponentModel.DescriptionAttribute.
• Add a new “no diagnostic” test ensuring short-form [Description] resolves to MSTest’s Microsoft.VisualStudio.TestTools.UnitTesting.DescriptionAttribute when only the MSTest namespace is imported, and is not incorrectly flagged.

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/DoNotUseSystemDescriptionAttributeAnalyzerTests.cs	Adds two edge-case unit tests covering DataTestMethod inheritance detection and MSTest [Description] short-name resolution without triggering the analyzer.

Copilot's findings

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