[test-improver] test: add edge case tests for NonNullableReferenceNotInitializedSuppressor

[Evangelink]

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Goal and Rationale

NonNullableReferenceNotInitializedSuppressor (MSTEST0028) had only 3 tests, each covering the positive "suppress" path or the basic "don't suppress" path. The suppressor's ReportSuppressions method has three independent guard conditions that must all be true to suppress a CS8618 diagnostic:

1. Property name must be "TestContext"
2. Property type must be TestContext (exact type match via SymbolEqualityComparer)
3. Containing type must have [TestClass] or a derived attribute (via Inherits())

Previously only condition 3 was tested via the "non-test-class" case. Conditions 1 and 2 had no dedicated "fail" path tests, and condition 3 was only tested with the base [TestClass] attribute (not a derived one).

Approach

Added four new tests:

Test	Condition exercised
TestContextPropertyOnClassWithDerivedTestClassAttribute_DiagnosticIsSuppressed	Condition 3 (positive): derived [TestClass] attribute triggers suppression via Inherits()
TestContextPropertyWithWrongTypeName_DiagnosticIsNotSuppressed	Condition 2 (negative): a class named TestContext of a different type is not suppressed
TestContextPropertyWithWrongPropertyName_DiagnosticIsNotSuppressed	Condition 1 (negative): a property of TestContext type but named MyContext is not suppressed

Trade-offs

Minimal maintenance burden — tests are straightforward suppressor verifications.

Reproducibility

./build.sh --test --projects "$(pwd)/test/UnitTests/MSTest.Analyzers.UnitTests/MSTest.Analyzers.UnitTests.csproj"

Test Status

✅ All tests passed (0 errors, 0 warnings, net8.0)

Generated by Test Improver · sonnet46 5.3M · ◷

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[Copilot]

Pull request overview

Adds additional unit tests for NonNullableReferenceNotInitializedSuppressor (MSTEST0028) in MSTest.Analyzers.UnitTests, expanding coverage of suppression guard conditions (derived [TestClass] attributes, wrong property name, and wrong property type).

Changes:

• Add a new test that validates suppression when [TestClass] is applied via a derived attribute.
• Add negative tests ensuring suppression does not occur when the TestContext property has the wrong type or the wrong property name.
• Extend expected diagnostic verification to cover the “wrong property name” case with correct CS8618 arguments.

Show a summary per file

File	Description
test/UnitTests/MSTest.Analyzers.UnitTests/NonNullableReferenceNotInitializedSuppressorTests.cs	Adds new edge-case unit tests for MSTEST0028 suppression behavior and strengthens negative-path coverage.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 3