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

SeleniumBase Case Plans is Test Case Management Software that uses Markdown tables for displaying test plans directly in GitHub (and other source code management systems that support Markdown format).

Free browser plugin to measures page load time and displays it in the toolbar.

The Apache JMeter™ application is open source software, a 100% pure Java application designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.

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

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