Jest is designed to ensure the correctness of any JavaScript codebase. It has a great API, is well maintained and well documented, and can be extended to meet your exact requirements. Simply put, Jest just makes testing delightful!
...By ensuring your tests have unique global state, Jest can reliably run tests in parallel. To make things quick, Jest runs previously failed tests first and re-organizes runs based on how long test files take. Jest uses a custom resolver for imports in your tests, making it simple to mock any object outside of your test’s scope. You can use mocked imports with the rich Mock Functions API to spy on function calls with readable test syntax.