Refactor String/Collection Assert code-fix scaffolding into shared base

[Copilot]

StringAssertToAssertFixer and CollectionAssertToAssertFixer had duplicated code-fix scaffolding (GetFixAllProvider, diagnostic-property extraction, invocation-node guards, and root replacement flow). This change consolidates that shared pipeline while preserving each fixer’s rule-specific rewrite behavior.

• Shared code-fix pipeline

  • Added AssertToAssertFixerBase with:
    • common GetFixAllProvider (BatchFixer)
    • unified RegisterCodeFixesAsync scaffold
    • optional FixKind property handling
    • shared invocation replacement helper

• String assert fixer migration

  • StringAssertToAssertFixer now derives from AssertToAssertFixerBase
  • Keeps only StringAssert-specific wiring and argument/member rewrite logic

• Collection assert fixer migration

  • CollectionAssertToAssertFixer now derives from AssertToAssertFixerBase
  • Keeps only CollectionAssert-specific FixKind routing and rewrite logic

public abstract class AssertToAssertFixerBase : CodeFixProvider
{
    public sealed override FixAllProvider GetFixAllProvider()
        => WellKnownFixAllProviders.BatchFixer;

    public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        // shared diagnostic/property extraction + invocation guards + CodeAction registration
    }

    protected abstract Task<Document> FixAssertAsync(
        Document document,
        InvocationExpressionSyntax invocationExpr,
        string properAssertMethodName,
        string? fixKind,
        CancellationToken cancellationToken);
}

[Copilot]

Pull request overview

This PR refactors duplicated Roslyn code-fix scaffolding from the MSTest analyzer code fixers into a shared base class, keeping the StringAssert/CollectionAssert-specific rewrite logic in their respective fixers.

Changes:

• Introduces AssertToAssertFixerBase to centralize common CodeFixProvider plumbing (FixAll provider, diagnostic property extraction, invocation guards, and CodeAction registration).
• Updates StringAssertToAssertFixer to derive from the new base and delegate into its existing StringAssert rewrite.
• Updates CollectionAssertToAssertFixer to derive from the new base, including optional FixKind handling, and delegate into its existing CollectionAssert rewrite.

Show a summary per file

File	Description
src/Analyzers/MSTest.Analyzers.CodeFixes/StringAssertToAssertFixer.cs	Migrates to the shared base and keeps only StringAssert-specific rewrite behavior.
src/Analyzers/MSTest.Analyzers.CodeFixes/CollectionAssertToAssertFixer.cs	Migrates to the shared base and retains fix-kind routing + CollectionAssert-specific rewrites.
src/Analyzers/MSTest.Analyzers.CodeFixes/AssertToAssertFixerBase.cs	Adds a shared code-fix pipeline used by both fixers.

Copilot's findings

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

[Evangelink]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved. The two conflicts were in CollectionAssertToAssertFixer.cs and StringAssertToAssertFixer.cs — both caused by main's commit #8846 moving ProperAssertMethodNameKey into AssertToAssertAnalyzerHelpers. I kept our refactored RegisterCodeFixesAsync delegation to the helper class and updated both key references to AssertToAssertAnalyzerHelpers.ProperAssertMethodNameKey. Build verified clean (0 errors, 0 warnings).