Jest's main job is to simplify unit testing (checking individual functions or components) and integration testing (checking how different parts of the application work together). What makes Jest stand out is that it provides a complete testing toolkit right out of the box, meaning you don't have to download and configure many other separate tools. For example, it includes built-in features for creating fake versions of parts of your system (mocking), and it automatically generates code coverage reports to show you which parts of your code are tested and which are not.

One of its most powerful features is Snapshot Testing. This capability allows Jest to take a "picture" of a rendered component's output. The next time you run your tests, it compares the new output to the old picture, instantly telling you if a change you made unintentionally broke the user interface. Finally, Jest is known for its speed. It runs tests at the same time (in parallel) and has a "Smart Watch Mode" that only re-runs tests affected by your latest code changes, which drastically shortens the time developers wait for results. This makes it an ideal tool for any modern development workflow, fitting perfectly into continuous integration and deployment pipelines. Reference : https://keploy.io/blog/community/jest-testing-top-choice-for-front-end-development