testing-tdd-refactor-guard

To prevent regressions during AI-assisted Swift refactoring, you need a safety check that verifies XCTest coverage before applying changes. This guard scans test targets, assesses coverage quality against thresholds, and generates characterization tests if existing coverage is insufficient to catch behavioral changes.

Characterization tests capture the current behavior of existing code before refactoring. You need them when test coverage is partial or missing, ensuring that accidental behavior changes during renames, extractions, or migrations are caught by failing regressions.

Checking XCTest coverage before a CoreData to SwiftData migration involves scanning test targets for XCTest patterns and evaluating test quality against defined thresholds. A characterization test generator is invoked to capture current behavior if the assessed coverage falls below required safety levels.

Yes, the refactor guard works with Apple-platform codebases lacking tests by triggering a characterization test generator. This generator instructs the creation of tests to capture current behavior, ensuring unsafe refactors are prevented even when initial XCTest coverage is completely missing.

The best way to evaluate test quality before extracting a public API in Swift is to scan test targets for XCTest patterns and assess whether tests validate behavior versus implementation. This ensures your coverage will catch regressions during the API reorganization.

AI-assisted refactoring fails without sufficient test coverage because there is no safety net to detect accidental behavior changes. Without XCTest patterns validating the public API surface, renames or extractions can introduce silent regressions requiring extensive debugging to resolve.