Top 25 API Testing Interview Questions

APIs are fundamental to modern applications, serving as the intermediary for communication between different software systems. Effective API testing is crucial as it can identify defects early in the development process, thereby reducing the cost and effort of fixing issues later. The shift-left approach allows for early API testing, even before the user interface is built, ensuring that the application's backend functionalities are sound. Interviewers often probe candidates on their understanding of API testing, which includes defining APIs, understanding the components of API requests, the importance of API testing, and the various types of API tests such as functional, performance, security, and reliability testing. A solid grasp of tools like Postman, SoapUI, and REST Assured is beneficial, as well as knowledge of handling authentication, dynamic values, and integrating tests into CI/CD pipelines. Additional API testing facets include contract testing, handling undocumented APIs, and conducting load testing to ensure APIs can handle anticipated traffic volumes. Prioritizing test cases for regression testing based on criticality, usage patterns, and defect history is also emphasized to maintain a robust and reliable application ecosystem.