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.

Hand-crafted lightweight Rest Client for testing APIs. Supports collections, environments, git collaboration and local storage.

Test, scrape, generate, and automate without the pain and expense of hosting your own headless browsers.

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

Postman is an API platform for building and using APIs. Postman simplifies each step of the API lifecycle and streamlines collaboration so you can create better APIs—faster.

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.