Browser and Mobile Automation Test Framework for Node.js

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

Website and mobile testing at every stage of development

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

HyperTest is a no-code test automation tool that regresses all your APIs by auto-generating integration tests using your network traffic, also giving a way to reproduce these failures inside actual user-journeys.

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.