React Testing Library

React Testing Library changed how we think about component tests. Instead of testing implementation details — state, hooks, internal methods — you test what users see and do. Query by text, role, or label. Click buttons. Check visible output. If a refactor doesn't change the user experience, the tests still pass. That's the whole philosophy.

Enzyme was the old way — shallow rendering and inspecting internal state. Testing Library won that war decisively. Playwright and Cypress handle end-to-end tests. Vitest or Jest run the test suite itself.

Use React Testing Library for every React component test. It's not a test runner (pair it with Vitest or Jest), but it's the standard for writing tests that don't break when you refactor. MIT-licensed, 19K stars, used everywhere.

The catch: if you genuinely need to test internal component state or hook behavior in isolation, Testing Library won't let you. That's by design — but some edge cases require reaching for lower-level tools. Also, the accessibility-first queries have a learning curve coming from Enzyme's selector-based approach.