API Testing interview Questions and Answers

API Testing interview Questions and Answers

Real-time API testing interview questions and answers tailored for experienced candidates. The first set includes fundamental questions (1 to 10), while the subsequent set covers scenario-based questions (11 to 25) to assess practical skills.

Could you explain API testing and provide a list of HTTP status codes?
How do you create an API test suite?

Can you outline the principles of API test design?
What are the key aspects to verify during API testing?
What are the most popular API testing tools?
What types of bugs can API testing find?
Can you define Postman? And Explain 3-Tier Architecture?
What is the process for adding validation points in Postman?
What are the commonly used test cases in API testing?
What are the reasons for favouring API testing over UI testing for automated tests?
You're testing an API that requires user authentication using JWT tokens. How would you verify that only authorized users can access certain endpoints?
You are testing an authentication API. Explain how you would use Postman to test different authentication methods like Basic Auth, OAuth2, and API tokens. What considerations should you keep in mind for each method?
The API documentation states that the service has rate limiting in place. How would you test the API to ensure that the rate limiting mechanism is working as intended?
The API you are testing requires testing different input data formats, such as JSON and XML. How can you configure Postman to send requests with different content types and validate the responses accordingly?
Suppose an API request results in an error response. How would you verify that the error response contains the correct HTTP status code, a clear error message, and possibly additional relevant information?
You're testing an API that accepts user input. What strategies would you use to ensure that the API handles both valid and invalid input properly, and that potential security vulnerabilities like SQL injection and XSS attacks are prevented?
You need to test APIs with multiple endpoints that have dependencies. How can you use Postman to set up test scenarios that involve chaining requests together and passing data between them?
You're testing an API that involves data manipulation operations (e.g., creating, updating, deleting records). How would you ensure data consistency across multiple related API calls?
The API supports webhooks to notify external systems of certain events. How would you test the webhook functionality, ensuring that the correct payloads are sent and received?
You need to test the API's performance under heavy load. What tools and strategies would you employ to simulate high traffic and measure response times, resource utilization, and potential bottlenecks?
How would you design a testing approach to validate that the API's monitoring and logging mechanisms are capturing relevant information, such as errors, performance metrics, and usage patterns?
During testing, you encounter an API response that includes dynamically generated values (e.g., timestamps, session IDs). How can you extract these values from one request's response and use them in subsequent requests within the same Postman collection?
How do you ensure test coverage validation and determine if coverage is comprehensive?
The API you are testing has rate limiting in place. Describe how you would use Postman to simulate requests that exceed the rate limit and observe how the API behaves. What kind of response codes or messages might you expect?
The API is frequently updated, and you want to automate regression testing. How can you create an automated test suite using Postman collections, Newman (Postman's command-line tool), and continuous integration tools?