Browser and Mobile Automation Test Framework for Node.js

Simulate APIs, integrations, and environments at enterprise scale.

Requestly is an open-source tool that simplifies API development, testing, mocking, and integration for developers and QAs.

Design, debug, and test APIs locally or in the cloud

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.

Free & OpenSource REST API Testing Tool for all levels in a Test Pyramid