What Is API Testing?

API testing is a type of software testing that validates Application Programming Interfaces (APIs). The purpose of API testing is to check the functionality, reliability, performance and security of programming interfaces. In API testing, instead of using standard user inputs(keyboard) and outputs, you use software to send calls to the API, receive output, and note the system’s response. API tests are different from GUI tests and do not concentrate on the look and feel of an application. It mainly focuses on the business logic layer of the software architecture.

What Is API?

API (Application Programming Interface) is a computing interface that provides communication and data exchange between two separate software systems. A software system that executes an API contains various functions/subroutines that another software system can perform. The API includes requests that can be made, how to create requests, data formats that can be used, and so on. definitions. between two software systems.

How to Test API

API automation testing should cover at least following testing methods apart from usual SDLC process

  • Discovery testing: The test group should manually execute the set of calls documented in the API like verifying that a specific resource exposed by the API can be listed, created and deleted as appropriate
  • Usability testing: This testing verifies whether the API is functional and user-friendly. And does API integrates well with another platform as well
  • Security testing: Security testing is a type of Software Testing that uncovers vulnerabilities, threats, risks in a software application and prevents malicious attacks from intruders.
  • Automated testing: API testing should culminate in the creation of a set of scripts or a tool that can be used to execute the API regularly
  • Documentation: The test team has to make sure that the documentation is adequate and provides enough information to interact with the API. Documentation should be a part of the final deliverable

Benefits of API testing

  • Earlier Tests 

With API testing, once the logic is developed, tests can be created to check the accuracy of responses and data. Isolated test cases without having to wait for various teams to finish their work or create applications


  • Easier Test Maintenance 

User interfaces can be applied to browsers, devices, display direction, etc.it constantly changes and moves depending on how it is accessed. This creates a nightmare scenario in which tests are constantly rewritten to keep up with the actual code in production. API changes are much more controlled and rare – often API definitions files, such as OpenAPI Spec, can help refactoring tests run for only a second.


  • Faster Time For Resolution 

When API tests fail, we know exactly where our system is broken and where the defect can be found. This helps reduce the triaging time of errors between structures, integrations and even different team members. The small, isolated footprint of an API test is perfect for faster MTTR statistics, a valuable KPI for DevOps teams.

  • Speed and test scope 

300 UI tests can take 30 hours to run. 300 API tests can be run in 3 minutes. This means that you will find more errors in less time and fix them immediately.