WHAT IS API TESTING?

API testing enables developers and testers to test the series of components that make up their application. Without API testing, they would be stuck manual testing, just like a user, testing the application at the UI level, waiting until the entire application stack is built before being able to start testing.

You can instead perform automated API testing by testing the application at the API level, designing test cases that interact directly with the underlying APIs, and gaining numerous advantages, including the ability to test the business logic at a layer that is easy to automate in a stable manner. Unlike manual testing, which is limited to validating a specific user experience, API testing gives you the power to bulletproof your application against the unknown. 

Testing earlier, at the API level, helps you “fail fast and fail early,” catching defects early at their source, rather than later in the software delivery process. API tests include service tests, contract tests, component tests, scenario tests, load/ performance tests, security tests, and omni-channel tests.