Robot Framework is a generic open source automation framework. It can be used for test automation and robotic process automation (RPA).

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

ReadyAPI is a low-code API testing platform for development teams that care about creating test automation across any workflow.

AI-Powered NoCodeTest Automation and Test Management on 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.

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