API Testing Interview Questions and Answers
Intermediate / 1 to 5 years experienced level questions & answers
Ques 1. What is API testing?
API testing involves testing the application programming interfaces (APIs) to ensure they meet functional and performance requirements.
Ques 2. Explain the difference between SOAP and RESTful APIs.
SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information, while REST (Representational State Transfer) is an architectural style based on a set of constraints. RESTful APIs are generally simpler and use standard HTTP methods.
Ques 3. Explain the concept of endpoint in API testing.
An endpoint is a specific URL where an API can be accessed. It represents the location where the resource can be found or manipulated.
Ques 4. What is the importance of authentication in API testing?
Authentication ensures that the API is accessed by authorized users only. Common authentication methods include API keys, OAuth, and JWT.
Ques 5. Explain the term 'Swagger' in the context of API testing.
Swagger is a tool that helps document and test APIs. It provides a standard way to describe RESTful APIs using a JSON or YAML format.
Ques 6. What is the role of the 'Authorization' header in API requests?
The 'Authorization' header is used to send credentials (such as API keys or tokens) with an HTTP request, allowing the server to authenticate the user.
Ques 7. How do you handle pagination in API testing?
Pagination is often handled using parameters like 'page' and 'per_page' in API requests to retrieve a specific subset of data. Testers need to ensure that pagination works correctly.
Ques 8. What is the purpose of the 'Content-Type' header in an HTTP request?
The 'Content-Type' header specifies the media type of the resource being sent or requested. Common values include 'application/json' and 'application/xml'.
Ques 9. Explain the term 'Mocking' in the context of API testing.
Mocking involves creating simulated responses from an API to test the behavior of an application without making actual calls to the real API. It helps in isolating the testing environment.
Ques 10. What are the advantages of automated API testing over manual testing?
Automated API testing offers faster execution, repeatability, broader coverage, and the ability to detect issues early in the development process.
Ques 11. What is the purpose of the 'Cache-Control' header in an HTTP response?
The 'Cache-Control' header specifies caching directives for both requests and responses. It controls how caching is applied to the resource.
Ques 12. Explain the concept of 'Rate Limiting' in API testing.
Rate limiting restricts the number of API requests a client can make in a given time period. It is used to prevent abuse, ensure fair usage, and maintain system stability.
Ques 13. What is the purpose of the 'Accept' header in an HTTP request?
The 'Accept' header indicates the media types that the client can understand. It helps the server provide an appropriate response format, such as JSON or XML.
Ques 14. Explain the term 'Webhooks' in the context of APIs.
Webhooks are HTTP callbacks that allow external systems to be notified in real-time when certain events occur. They are often used for event-driven architectures.
Ques 15. What is the purpose of the 'Location' header in an HTTP response?
The 'Location' header is used in the HTTP response to provide the URL of the newly created or modified resource, especially in the case of a successful POST request.
Ques 16. How do you handle API versioning to ensure backward compatibility?
API versioning is often done using URL versioning, custom headers, or request parameters. Testers need to ensure that changes in versions do not break existing functionality.
Ques 17. What is the purpose of the 'OPTIONS' HTTP method?
The 'OPTIONS' method is used to describe the communication options for the target resource. It is often used to support cross-origin resource sharing (CORS).
Ques 18. What is the purpose of the 'ETag' header in an HTTP response?
The 'ETag' header provides a mechanism for caching and conditional requests. It represents a unique identifier for a specific version of a resource.
Ques 19. How do you handle testing for paginated APIs?
Testing paginated APIs involves verifying that the pagination parameters work correctly, ensuring that the correct number of items is returned per page, and testing the behavior of pagination links.
Ques 20. How can you ensure data integrity in API testing?
Data integrity in API testing can be ensured by validating the correctness and consistency of data returned by the API. This includes checking data types, formats, and values.
Ques 21. What is the purpose of the 'HEAD' HTTP method?
The 'HEAD' method is similar to GET but returns only the headers and no message body. It is often used to check the status and headers of a resource without fetching the entire content.
Ques 22. Explain the concept of 'Swagger Codegen' in API development.
Swagger Codegen is a tool that automatically generates server stubs and client libraries from an OpenAPI Specification. It helps in accelerating API development.
Ques 23. What is the purpose of the 'Retry-After' header in an HTTP response?
The 'Retry-After' header indicates how long the client should wait before making another request. It is often used in the context of rate limiting or when a server is temporarily unavailable.
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