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

REST API client library for .NET

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.

Browser and Mobile Automation Test Framework for Node.js

Testing and validating REST services in Java is harder than in dynamic languages such as Ruby and Groovy. REST Assured brings the simplicity of using these languages into the Java domain.