Mockoon is the easiest and quickest way to design and run mock REST APIs.

Percy is a visual testing and monitoring tool that focuses on detecting visual changes in web applications

Hoppscotch is an open-source API development ecosystem that helps you create and test your API requests saving precious time in development.

RapidAPI for Mac is a full-featured HTTP client that lets you test and describe the APIs you build or consume. It has a beautiful native macOS interface to compose requests, inspect server responses, generate client code and export API definitions.

The Complete Continuous Testing Platform Any test. Any device. App quality without limits.

Jest is a delightful JavaScript Testing Framework with a focus on simplicity.