Skill UI

This guide provides comprehensive patterns for migrating Enzyme unit tests to React Testing Library (RTL), especially when upgrading to React 18. It emphasizes the crucial philosophical shift from testing internal implementation details (like state or props) to asserting visible user behavior. Learn best practices for rewriting shallow/mount/simulate calls into modern, accessible, and resilient RTL queries, ensuring your tests reflect how a user genuinely interacts with the component.

This guide provides the complete, step-by-step migration pattern for outdated React context APIs (such as contextTypes, childContextTypes, and getChildContext) to the modern createContext API. Since context migration is always a cross-file process, this skill emphasizes the required coordination between the provider and all consumer components to prevent runtime failures and correctly update the entire application codebase.

Provides a comprehensive reference for migrating deprecated and unsafe class component lifecycle methods (such as componentWillMount, componentWillReceiveProps, and componentWillUpdate) to modern, React 18 compliant patterns. This guide is essential when updating legacy codebases, helping developers correctly identify the semantic purpose of the method and choose the correct replacement hook (e.g., componentDidMount or getDerivedStateFromProps), thus preventing common migration errors.

This skill provides comprehensive migration patterns for handling deprecated string refs in React (e.g., ref="name" + this.refs.name). As string refs are removed in React 19, this guide details how to safely migrate all usage—including single element refs, list refs, and callback refs—to the modern, recommended pattern using React.createRef(). It ensures developers can update their codebase for robust compatibility with React 18 and beyond.

A comprehensive reference for diagnosing and fixing silent breaking changes in React 18 class components. This guide covers how React 18 automatically batches state updates in asynchronous contexts (e.g., setTimeout, Promises, async/await), providing patterns for handling state reads after awaiting, and offering guidance on when to correctly use `flushSync` versus refactoring.

Guides preserving React 18 concurrent patterns during migration to React 19 while outlining post-migration adoption of new APIs like use(), Actions, useOptimistic, and Suspense data fetching so concurrent behavior stays intact.