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

Burp or Burp Suite is a set of tools used for penetration testing of web applications. It is developed by a company named Portswigger who make freely available a Web Security Academy which has a range of lessons on penetration testing.

Fully integrated API and web service testing capabilities that automate end-to-end functional API testing.

Streamline your API testing, integration testing and test data management.

Swagger UI allows anyone — be it your development team or your end consumers — to visualize and interact with the API’s resources without having any of the implementation logic in place

Puppeteer is a Node.js library which provides a high-level API to control Chrome/Chromium over the DevTools Protocol.