Jest is a unit testing framework.
- Instant feedback: Fast interactive watch mode runs only test files related to changed files and is optimized to give signal quickly.
- Snapshot testing: Capture snapshots of React trees or other serializable values to simplify testing and to analyze how state changes over time.
One of Jest’s philosophies is to provide an integrated “zero-configuration” experience. We observed that when engineers are provided with ready-to-use tools, they end up writing more tests, which in turn results in more stable and healthy codebases.