50 API Testing Interview Questions and Answers

Edited By Team Careers360 | Updated on Apr 15, 2024 05:44 PM IST | #Manual Testing

API testing is a crucial aspect of software development that ensures the proper functioning and integration of different software components. As software development is one of the sought-after fields to pursue a career, you must prepare for the interview process. In this article, we will explore the top 50 API testing interview questions and answers apt for both freshers and experienced professionals. These cover a comprehensive understanding of testing concepts and methodologies. Several online software testing certification courses can develop your knowledge in this field.

This Story also Contains

Basic API Testing Interview Questions
Intermediate API Testing Interview Questions And Answers
Explore Software Testing Certification Courses by Top Providers
Advanced API Testing Interview Questions And Answers
Explore the Top Testing Certification Courses
Conclusion

50 API Testing Interview Questions and Answers

API Testing involves evaluating Application Programming Interfaces (APIs) to verify their performance, functionality, and integration capabilities. It ensures that APIs transmit data accurately and facilitate smooth interactions between various software modules. A strong grasp of API testing is indispensable for testers to validate the reliability, correctness, and efficiency of APIs. Let us get started with the must-know API testing interview questions and answers for freshers and experienced professionals.

Basic API Testing Interview Questions

Q.1 What is an API, and why is API testing important?

This is one of the most common API testing interview questions. API stands for Application Programming Interface, a set of protocols and tools that enable different software applications to communicate. API testing ensures seamless data exchange and system integration.

Q.2 Differentiate between API testing and GUI testing.

API testing focuses on testing code-level communication between software components, while GUI testing validates user interfaces and interactions. This is an important topic you must practise for better API testing interview questions and answers preparation

Q.3 What are the common HTTP methods used in API testing?

This is amongst the top API testing interview questions for freshers. Common HTTP methods include GET, POST, PUT, DELETE, PATCH, and HEAD. These methods perform actions like retrieving, creating, updating, and deleting data.

Q.4 Explain the role of status codes in API responses.

Status codes indicate the outcome of an API request. For instance, 200 indicates success, 404 signifies not found, and 500 denotes a server error. This type of API testing interview questions and answers are frequently asked in interviews.

Q.5 How do you handle authentication in API testing?

Authentication can be managed using Basic Authentication (username and password), Token-based Authentication (JWT tokens), or OAuth for secure API access. This is another one of the must-know API testing interview questions for freshers.

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Q.6 What is the purpose of API documentation?

API documentation serves as a comprehensive user manual for an API, offering clear instructions on how to interact with it effectively. It details crucial information such as API endpoints, the expected formats for requests and responses, specific parameters to be included, and any authentication methods necessary for successful utilisation. This documentation ensures that developers can seamlessly integrate and utilise the API while minimising errors and misunderstandings.

Q.7 What is API versioning, and why is it important?

This is one of the API testing basic interview questions you must prepare. API versioning maintains multiple versions of an API to accommodate changes without disrupting existing consumers, ensuring compatibility and smooth transitions.

Q.8 How do you ensure data integrity in API testing?

Data integrity in API testing is upheld through a meticulous process of verification where the data transmitted in API requests aligns precisely with what is received in the ensuing responses. This validation step guarantees that the information exchanged between software components remains consistent, reliable, and error-free. This type of API Testing interview questions is often asked by interviewers to test your understanding of data integrity.

Q.9 How can you validate JSON responses in API testing?

This is one of the topics that must be in your API testing interview questions and answers preparation list. To validate JSON responses in API testing, employ dedicated tools like JSON Schema Validator or utilise programming language libraries. These tools ensure the correctness of the JSON structure and its content, aiding in comprehensive data validation during testing processes.

Q.10 What are query parameters in API requests?

This is one of the common API testing interview questions for freshers. Query parameters are additional data sent with the URL to filter, sort, or modify API responses. They are commonly used in GET requests.

Intermediate API Testing Interview Questions And Answers

Q.11 What is POSTman, and how does it aid in API testing?

POSTman, a widely used API testing tool, plays a pivotal role in streamlining API testing processes. It empowers testers by simplifying the generation, organisation, and execution of API requests through its user-friendly interface, making the testing experience highly intuitive and efficient. This is one of the must-know API testing interview questions for freshers as well as experienced testers.

Q.12 How do you handle pagination in API testing?

In API testing, pagination is effectively managed by scrutinising the response headers, often labeled as 'Link' or 'Next-Page,' which provide essential information about fetching subsequent data. Subsequent requests are then meticulously crafted based on this header data to ensure the retrieval of additional relevant information. This method guarantees comprehensive testing of data retrieval mechanisms, especially in scenarios involving large datasets.

Q.13 What are API test assertions, and why are they important?

This is amongst the important API related interview questions. API test assertions validate expected outcomes against actual responses, ensuring the correctness of API behaviour.

Q.14 How can you handle time-sensitive API testing scenarios?

This one of the API testing interview questions must be in your preparation list. Handling time-sensitive API testing scenarios often requires creative solutions. Mock APIs and virtualization tools help simulate time-bound responses, ensuring accurate testing. Additionally, adjusting system clocks to mimic various time zones can replicate real-world scenarios for comprehensive testing.

Q.15 Explain the concept of API mocking.

API mocking is a practice where simulated API responses are created to replicate the behaviour of real APIs. This technique is invaluable in scenarios where the actual APIs are inaccessible or under development. By mimicking authentic responses, API mocking facilitates comprehensive and independent testing, ensuring software components can function seamlessly even before the actual APIs are fully operational. This type of API testing interview questions and answers are often asked in interviews.

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Q.16 What is contract-first API testing?

This is one of the common API testing interview questions for experienced professionals as well as freshers. Contract-first testing involves creating API contracts (OpenAPI or Swagger documents) before implementation, ensuring alignment between design and development.

Q.17 What is API load testing, and why is it essential?

API load testing is an important topic that you should practise for better API testing interview questions and answers preparation. API load testing evaluates an API's performance under various load conditions to determine its scalability, responsiveness, and reliability.

Q.18 How do you manage API dependencies in testing?

In API testing, the management of API dependencies is crucial for conducting thorough and controlled tests. This involves strategies such as creating mock or stub versions of dependent APIs to simulate their behaviour, ensuring testing continuity even when the actual APIs are inaccessible. Additionally, setting up dedicated integration environments can facilitate comprehensive testing of API interactions.

Q.19 How can you perform API testing in different environments?

It can be performed by using environment-specific configurations or tools like environment variables to switch between development, testing, and production environments. This type of API testing interview questions is important for preparation to better perform in interviews.

Q.20 What is boundary testing in API testing?

This is amongst the frequently-asked API testing interview questions for freshers. Boundary testing involves testing API inputs at the lower and upper boundaries of valid ranges to identify potential vulnerabilities.

Q.21 What is API monitoring, and why is it important?

API monitoring is a crucial topic you should know while preparing for API testing interview questions for experienced. It involves continuously tracking API performance and availability. It is crucial to detect issues proactively, ensuring a seamless user experience.

Q.22 Explain the concept of API contract testing, and how is it different from functional testing.

API contract testing focuses on validating whether an API complies with its documented contract (e.g., OpenAPI). Functional testing, on the other hand, verifies the functionality and behaviour of the API. This is one of the top API testing interview questions for freshers and experienced.

Q.23 What are the advantages of using API testing frameworks like Postman or RestAssured?

API testing frameworks like Postman or RestAssured offer a range of benefits. They come equipped with pre-designed functions, ready-to-use test suites, and automation features. This not only simplifies the testing process but also significantly amplifies test coverage, making them invaluable tools for efficient and thorough API testing.

Q.24 How can you ensure data privacy and security in API testing?

This is amongst the most asked API testing interview questions for experienced professionals. Data privacy and security can be maintained by using encryption (HTTPS), tokenization, and adhering to data protection regulations like GDPR during API testing.

Q.25 What is the purpose of API request headers, and how do you test them?

API request headers carry metadata or instructions for the server. Testing headers involves sending various header values to ensure the API responds correctly. You must know this topic and practise while preparing for API testing interview questions and answers.

Q.26 In API testing, how can you evaluate the robustness of error handling?

Assessing the robustness of error handling in API testing involves intentionally introducing various error scenarios. You can manipulate input data, send malformed requests, exceed rate limits, or provoke specific error codes like 403 (Forbidden) or 401 (Unauthorised). This comprehensive testing approach ensures that the API gracefully handles errors, providing a resilient user experience even in adverse conditions.

Explore Software Testing Certification Courses by Top Providers

Q.27 What is API discovery, and why is it relevant in testing?

API discovery is another important topic to understand for effective API testing interview questions and answers preparation. This is the process of actively identifying and comprehending the various APIs existing within a software system or ecosystem. In the context of testing, it holds significance by guaranteeing that all APIs are recognised and assessed, ensuring that testing efforts encompass the entire API landscape for thorough evaluation and validation.

Q.28 How can you automate API testing for regression testing?

This is amongst the top API testing interview questions for experienced professionals. Automation tools like Postman, RestAssured, or API testing libraries in programming languages allow you to create and execute automated tests, making regression testing efficient and reliable.

Q.29 What is contract-first testing, and when is it preferred over code-first testing?

Contract-first testing involves creating API contracts (OpenAPI or Swagger documents) before implementation. It is preferred when multiple teams or third-party integrations need to align with the API design. You must prepare for this type of API Testing interview questions.

Q.30 What is the role of API gateways in API testing?

This one of the important API Testing interview questions will test your in-depth understanding of API testing. API gateways act as intermediaries between clients and APIs, handling tasks like authentication, rate limiting, and logging. In testing, API gateways must be validated for proper functionality.

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Advanced API Testing Interview Questions And Answers

Q.31 What is API security testing, and why is it crucial?

This is one of the advanced API testing interview questions to prepare for. API security testing is a vital practice that scrutinises APIs to identify and rectify potential security weaknesses such as injection attacks, data leaks, and unauthorised access. This process is indispensable for safeguarding data integrity and upholding the overall security of systems and applications.

Q.32 How can you handle testing APIs with third-party integrations?

This is another one of the advanced API testing interview questions for experienced individuals. Testing APIs with third-party integrations involves creating mock APIs or using API virtualization tools to simulate responses from external systems.

Q.33 Explain the concept of stateful API testing.

Stateful API testing focuses on evaluating APIs that retain data or context across multiple requests. This typically includes scenarios where user sessions or authentication tokens are utilised to maintain continuity, and testing ensures that these persistent states function correctly throughout the API interactions. This type of API testing interview questions and answers is frequently asked in interviews.

Q.34 What is the role of API version deprecation, and how should it be managed in API development?

API version deprecation is the process of phasing out older versions of an API in favour of newer ones while ensuring a smooth transition for consumers. It should be managed through clear communication with developers, providing ample time for migration, and offering support during the transition. This helps maintain backward compatibility and minimises disruptions for existing users.

Q.35 What is mutation testing in API testing?

Mutation testing involves introducing small changes (mutations) to API code to assess the effectiveness of test cases in detecting these changes. API testing interview questions like this are crucial to understanding API and acing the interview.

Q.36 What is the significance of API rate limiting, and how does it impact API performance?

This is one of the important API testing interview questions and answers for experienced professionals. API rate limiting is crucial for controlling the number of requests a client can make to an API within a specified time frame. It safeguards the API from abuse or overuse, ensuring fair usage and preventing server overload. Proper rate limiting enhances API performance by maintaining a balance between accessibility and resource utilisation, providing a smoother experience for all users.

Q.37 What are webhook endpoints, and how do you test them?

Webhook endpoints are URLs used to receive real-time data notifications. Test them by triggering events and verifying the expected responses. This is amongst the advanced API testing interview questions you should practice for better preparation to crack your interview.

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Q.38 How can you ensure backward compatibility in API testing?

This is another one of the advanced API testing interview questions and answers you must learn. Test both old and new versions of APIs simultaneously to ensure backward compatibility and prevent disruptions to existing consumers.

Q.39 Explain the concept of testing API contracts.

Testing API contracts is the process of rigorously verifying that the real-world responses from an API align precisely with the predefined schema outlined in API contracts, such as Swagger or OpenAPI documents. This ensures that the API consistently delivers data and functionality as per the agreed-upon specifications, enhancing reliability and compatibility.

Q.40 What are the best practices for documenting API testing scenarios?

This type of API testing interview questions and answers are essential for effective preparation. Document API testing scenarios with clear test cases, request and response examples, expected outcomes, and any special considerations.

Q.41 What is API mocking, and why is it valuable in testing?

API mocking involves simulating API responses to mimic real behaviour, enabling testing even when actual APIs are unavailable. It is valuable for isolated testing and reducing dependencies. This type of topics are often asked during interviews, thus, you must include this in your API testing interview questions and answers preparation list.

Q.42 What are the advantages of using Swagger or OpenAPI documents in API testing?

This is amongst the advanced API testing interview questions you must know for better preparation. Swagger or OpenAPI documents provide a clear and standardised way to define API contracts, making it easier to generate documentation, validate requests and responses, and ensure consistency.

Q.43 How do you handle asynchronous API calls in testing?

Testing asynchronous API calls may require techniques like callback functions, promises, or asynchronous testing libraries to ensure that data is received and processed correctly. This is one of the must-know API testing interview questions for experienced testers.

Q.44 What is the purpose of rate limiting in API testing, and how can it be tested?

Rate limiting controls the number of API requests a client can make in a specific time frame. It can be tested by exceeding rate limits intentionally and verifying that the API responds appropriately. You must practise this type of API testing interview questions and answers to better perform during your interview.

Q.45 What is SOAP, and how does API testing for SOAP differ from REST?

SOAP (Simple Object Access Protocol) is a protocol for exchanging structured information in the implementation of web services. API testing for SOAP often involves XML-based requests and responses, while REST uses JSON or XML. This one of the API testing interview questions and answers is important to learn and understand to ace your interview.

Q.46 How can you handle API testing for a microservices architecture?

This is another important topic you must know while preparing for API testing interview questions and answers. API testing for microservices involves testing individual services, and service interactions, and ensuring that the entire system functions seamlessly. Tools like Docker and Kubernetes can assist in testing microservices.

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Q.47 What is mutation testing in the context of API testing, and how does it improve test coverage?

Mutation testing is one of the important topics that you should know for preparation of your API testing interview questions and answers. It involves making small changes (mutations) to API code to assess whether test cases can detect these changes. It helps identify weak spots in test coverage.

Q.48 Explain the concept of API contract versioning and its significance.

API contract versioning is managing different iterations of API contracts, like OpenAPI documents, to accommodate gradual modifications while preserving backward compatibility. This is essential to ensure a seamless transition when implementing updates to APIs, preventing disruptions for existing consumers and maintaining a stable user experience. This is one of the API testing interview questions that is often asked in interviews.

Q.49 How can you implement API testing as part of a continuous integration (CI) and continuous deployment (CD) pipeline?

This is amongst the essential topics that you must include in your API testing interview questions and answers preparation list. API testing can be integrated into CI/CD pipelines by automating tests using tools like Jenkins or Travis CI, ensuring that APIs remain reliable and functional throughout the development process.

Q.50 What is API virtualization, and why is it beneficial in testing?

API virtualisation involves creating virtual APIs that mimic real API behaviour, allowing testing even when the actual APIs are in development or unavailable. It accelerates development and testing cycles.

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Conclusion

API testing is paramount for ensuring the efficiency and integration of software components. By going through these API testing interview questions and answers, you can confidently tackle interviews and showcase your expertise in this critical field. Continuous learning and staying updated with industry trends will further solidify your skills as an API testing professional.

Frequently Asked Questions (FAQs)

1. Can I start API testing without programming knowledge?

While programming knowledge is beneficial, you can start with basic API testing concepts and gradually learn programming as you progress. This is yet again API testing interview questions and answers

2. What tools are commonly used for API testing?

Commonly used API testing tools include POSTman, RestAssured, SoapUI, and tools specific to programming languages like Python's requests library.

3. Is API testing only for experienced testers?

Both beginners and experienced testers can engage in API testing. Beginners can start with foundational concepts, while experienced testers can delve into advanced topics.

4. How does API testing contribute to software security?

API testing identifies security vulnerabilities like injection attacks, improper data validation, and unauthorised access, ensuring data security and system integrity.

5. What is the future scope of API testing?

As software development continues to rely on APIs for integration, the demand for skilled API testers will remain high, creating ample career opportunities.