Jest is a JavaScript testing framework developed by Meta (formerly Facebook) that has become the industry standard for testing JavaScript applications, especially in the React ecosystem. It provides a zero-configuration setup with built-in test runner, assertion library, mocking utilities, and code coverage tools—all in one package. Jest runs tests in parallel for speed, includes powerful snapshot testing for UI components, and offers an intuitive API that makes writing tests feel natural. The key advantage: Jest brings everything you need for comprehensive testing without juggling multiple tools, from unit tests to integration tests, making it ideal for both small projects and large-scale applications.

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