API testing has focused chiefly on message layer testing, which covers REST APIs and SOAP Web services that can be sent through HTTP, HTTPS, JMS, and MQ. This is now an essential part of any Automation Testing. APIs are used in some way in almost every application nowadays. Before releasing a product to a client or end-user, APIs must be adequately tested as a form of communication. Some testers skip over this stage and go right towards UI testing.