[test-improver] test: add edge case tests for PreferTestMethodOverDataTestMethodAnalyzer (MSTEST0044)

[Evangelink]

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Goal and Rationale

PreferTestMethodOverDataTestMethodAnalyzer (MSTEST0044) had 6 tests. Three behavioral boundaries were untested:

1. Fixer + [DataRow] coexistence — developers often use [DataTestMethod] because they think it's required for [DataRow] to work; the fixer should replace it with [TestMethod] while leaving all [DataRow] attributes untouched.
2. Method outside [TestClass] — the analyzer does not gate on test-class context; the diagnostic fires regardless of whether the containing class is a test class.
3. Two-level inheritance — the AnalyzeNamedType path uses Equals(namedTypeSymbol.BaseType, ...) (not .Inherits(...)), so only direct children of DataTestMethodAttribute are flagged; a grandchild class is not.

Approach

Added three new tests to PreferTestMethodOverDataTestMethodAnalyzerTests.cs:

Test	What it exercises
WhenDataTestMethodUsedWithDataRowAttribute_FixerPreservesDataRow	Code-fix preserves [DataRow] siblings
WhenDataTestMethodUsedOutsideTestClass_Diagnostic	Diagnostic fires on non-[TestClass] methods
WhenClassInheritsTwoLevelsFromDataTestMethod_OnlyDirectInheritanceIsFlagged	Only direct DataTestMethodAttribute inheritance is flagged

Test Status

Test run summary: Passed! (net8.0|x64)
  total: 9
  failed: 0
  succeeded: 9
  skipped: 0

Trade-offs

• No production code changes — tests only.
• The two-level inheritance test uses a non-sealed intermediate class (required so it can be subclassed), matching the real-world scenario.

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[Copilot]

Pull request overview

Adds targeted unit tests for the MSTest analyzer MSTEST0044 (PreferTestMethodOverDataTestMethodAnalyzer) to cover previously untested behavioral boundaries in the analyzer + code fix.

Changes:

• Adds a code-fix test ensuring [DataRow] attributes are preserved when [DataTestMethod] is replaced with [TestMethod].
• Adds a diagnostic + code-fix test confirming the analyzer fires even when the containing class is not marked [TestClass].
• Adds an analyzer scenario test covering two-level inheritance from DataTestMethodAttribute (only the direct child should be flagged).

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/PreferTestMethodOverDataTestMethodAnalyzerTests.cs	Adds three new edge-case tests for MSTEST0044 covering fixer behavior, non-test-class methods, and direct-vs-indirect inheritance.

Copilot's findings

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