API’s are the intermediate between the presentation layer and the database layer of a system, and it is the primary factor that completely integrates the systems together. API acts as a messenger that takes requests to the system, returning back with a response based on the intended command.
API Testing Services is carried out either directly or as a part of integration testing to determine if they meet the expectations as per the defined specification in terms of functionality, performance, and security. During the API testing, the data is exchanged from XML or JSON through HTTP requests and responses. API tests are performed at the business layer even before the GUI of the application is arrived; this helps to fix bugs and validate logical issues at the early stages of the application development lifecycle without being dependent upon the arrival of the UI.