Jest is a popular JavaScript testing framework used in almost every project nowadays. Jest uses a custom [haste module system] for building metadata about the files and dependencies between them in an optimized way. Instead of running an entire set of tests every time you are about to commit a new change, Jest will run only tests that are actually impacted by corresponding change saving developers a great amount of time.
Ildar Sharafeev
@isharafeev
Sr Software Engineer. decade+ in the industry. Passionate about frontend, micro-frontends, serverless, and clean code.