Deduplicate String/Collection assert analyzer scaffolding via shared base class

[Copilot]

CollectionAssertToAssertAnalyzer and StringAssertToAssertAnalyzer had near-identical structural boilerplate (diagnostic property key, SupportedDiagnostics, Initialize, and invocation preamble). This change extracts that shared analyzer scaffolding while preserving each analyzer’s rule-specific mapping logic.

• Shared analyzer infrastructure

  • Added AssertToAssertAnalyzerBase to centralize:
    • ProperAssertMethodNameKey
    • common SupportedDiagnostics implementation
    • common Initialize registration flow (CompilationStart + OperationKind.Invocation)
    • common invocation/type guard helper (TryGetTargetMethod)

• Analyzer refactor

  • Updated:
    • StringAssertToAssertAnalyzer
    • CollectionAssertToAssertAnalyzer
  • Both now provide only rule-specific pieces (DiagnosticRule, source assert type metadata name, and analyzer-specific invocation mapping).

• Code-fix alignment

  • Updated both fixers to read ProperAssertMethodNameKey from the shared base class, removing duplicated key ownership assumptions.

public abstract class AssertToAssertAnalyzerBase : DiagnosticAnalyzer
{
    internal const string ProperAssertMethodNameKey = nameof(ProperAssertMethodNameKey);

    public sealed override void Initialize(AnalysisContext context)
    {
        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
        context.EnableConcurrentExecution();
        context.RegisterCompilationStartAction(context =>
        {
            if (!context.Compilation.TryGetOrCreateTypeByMetadataName(SourceAssertTypeMetadataName, out INamedTypeSymbol? sourceAssertTypeSymbol))
                return;

            context.RegisterOperationAction(
                context => AnalyzeInvocationOperation(context, sourceAssertTypeSymbol),
                OperationKind.Invocation);
        });
    }
}

[Copilot]

Pull request overview

This PR refactors MSTest analyzer infrastructure by extracting shared scaffolding from the StringAssertToAssertAnalyzer and CollectionAssertToAssertAnalyzer into a common base class, while keeping each analyzer’s rule-specific mapping logic intact.

Changes:

• Introduced AssertToAssertAnalyzerBase to centralize common analyzer setup (supported diagnostics, initialization, and invocation filtering).
• Refactored StringAssertToAssertAnalyzer and CollectionAssertToAssertAnalyzer to inherit from the new base and only implement rule-specific behavior.
• Updated both code-fix providers to read the diagnostic property key from the shared base instead of each analyzer type.

Show a summary per file

File	Description
src/Analyzers/MSTest.Analyzers/AssertToAssertAnalyzerBase.cs	Adds shared analyzer scaffolding for “legacy assert type → Assert” migration analyzers.
src/Analyzers/MSTest.Analyzers/StringAssertToAssertAnalyzer.cs	Refactors analyzer to inherit from shared base and provide only string-assert-specific mapping.
src/Analyzers/MSTest.Analyzers/CollectionAssertToAssertAnalyzer.cs	Refactors analyzer to inherit from shared base and provide only collection-assert-specific mapping.
src/Analyzers/MSTest.Analyzers.CodeFixes/StringAssertToAssertFixer.cs	Switches property-key lookup to use the shared base constant.
src/Analyzers/MSTest.Analyzers.CodeFixes/CollectionAssertToAssertFixer.cs	Switches property-key lookup to use the shared base constant.

Copilot's findings

• Files reviewed: 5/5 changed files
• Comments generated: 1