What is API Testing?

API testing is a form of software testing that is used to analyze an application program interface or API. This is done for the verification of the program to check its reliability, performance, security, and functionality. The tests are done as a part of integration testing or on the API. An API is the middleware code that makes two software programs communicate and interact with each other. The applications have different layers, including:


  • A data layer
  • A service layer
  • An API later
  • The presentation layer is also known as the user interface or UI.

API testing is done by using API Tester, and it focuses on the analysis of businesses and the security of the data responses and applications. The API test is done by making requests to single or multiple API endpoints and comparing the response with the results to be expected.

Approaching API testing

Usually, the API testing is done, and it starts with a defined scope. It is done by checking the program’s scope and understanding the API’s functioning. The testers ask some questions, and these include.

  • What are the available endpoints for testing?
  • What are the response codes that are expected for successful requests?
  • What are the response codes that are expected for unsuccessful requests?
  • What are the error messages that are expected to appear in an unsuccessful request?

After understanding these factors, the testers can apply different testing techniques. The tests are done to analyze different responses, such as error codes, HTTP status codes, authorization and confirmation, data quality, and reply time.

API testing effectively checks different endpoints, such as web user interfaces, databases, and web services. The testers watch the unexpected or failed inputs. The response time should be up to an acceptable limit, and the API should be protected against different attacks.