API Testing Interview Questions For Freshers

1. What is an API?

Application Programming Interface (API) is useful for communication between different software systems. It acts as an interface between two applications and allows two software systems to communicate with one another.

• It is a collection of functions that can be executed by another software program.
• It takes the request from the user and gives the response without exposing the internal details.

2. What is API Testing?

API testing is a type of software testing that aims to test the API directly and as a part of integration testing to determine if it meets the expectations for functionality, performance, and security. It aims to analyze multiple endpoints such as databases, web services, etc.

3. List the differences between API and Web Service.

4. How do APIs work?

• API takes requests from the user.
• It processes the request which may involve data validation, data processing, database interaction, etc.
• The response is sent back to the source.

5. What are the different types of API testing?

1. Functional Testing: This aims to verify the API functions correctly and meets the required specifications.
2. UI Testing: This aims to validate that the API is returning the expected results and in the correct format.
3. Load Testing: This type of testing aims to test the APIs performance and stability under stressful conditions.
4. Security Testing: This type of testing aims to identify the security-related vulnerabilities and flaws in the API and ensures that the API meets the required security standards.
5. Validation Testing: This type of testing aims to ensure that the API is returning the expected results and in the correct format.
6. Runtime and Error Detection: This type of testing aims to ensure that the API can handle runtime errors and exceptions by testing for network timeouts, memory leaks, etc.
7. Penetration Testing: This is a type of security testing that involves simulating attacks from hackers to detect vulnerabilities and weaknesses in the API.
8. API Hacking: It is a security testing technique that exploits vulnerabilities in an API, Attackers can target API endpoints to gain access to data or disrupt services.
9. Fuzz Testing: It involves giving invalid inputs into the API to test its ability to handle unexpected input and recover from errors.

6. What protocols can be tested using API Testing?

• HTTP
• REST
• SOAP
• JMS
• UDDI

7. What are the advantages of API Testing?

• Faster bug fixes: API testing works quickly to provide a solution, thus it helps to diagnose problems earlier in the development of the system allowing for efficient bug detection and removal.
• Reduced costs: API testing provides quick release of results, easier to maintain, thus reducing the cost of testing.
• Universal language support: API testing provides support for many different languages like Javascript, Ruby, Python, and PHP. Formats like XML, and JSON are supported during API testing.
• Better test coverage: API testing provides better test coverage as it drills down to the layers beneath the UI to ensure databases are communicating correctly with one another.

8. What are the disadvantages of API Testing?

• Technical skills: API testing requires skilled and trained testers
• Time-consuming: API testing is time-consuming as it requires time to develop and execute test scripts for APIs.
• Limited documentation: Limited documentation of the API makes it difficult for the testers to understand how the API should behave in response to a particular input.
• Cost: API testing using automated tools can be expensive and requires a significant budget thus increasing the cost of testing.
• Security: APIs can introduce security vulnerabilities if not properly tested and secured.

9. List the differences between API Testing and Unit Testing.

10. What needs to be verified in API testing?

• API testing helps to verify the correctness of data and responses. The API should return the return correct data and resposnses according to the specified requirements and expected behavior.
• API testing should verify the functionality and behavior. The API should perform its intended functions accurately.
• HTTP status codes of the API needs to verified.
• Error codes if the APIs are expected to throw an error.
• Authorization details.

11. What is Latency in API testing?

Latency in API testing is how long it takes for the request to reach the server. The shorter the response time, the better the user experience.

12. What is an API framework?

API framework is a foundation on which a software developer can build applications for a specific platform. It is defined by the configuration file which consists the list of all APIs that is reqquired to be activated and activated for a particular program run.

13. Mention common HTTP methods used in API testing.

• POST: It is used to create new data or resources on an API.
• GET: It is used to retrieve data or resources from an API.
• PUT: It is used to update existing data or resources on an API.
• PATCH: It is used to update existing data or resources from an API partially.
• DELETE: It is used to delete data or resources from an API.

14. What is the role of headers in API testing?

Headers in API testing plays an important role in providing additional information that is not included in the request body. Herders are important in controlling the behavior of the server in handling the request, to provide authentication information, or to provide metadata about the request or response.

15. What is the purpose of authentication in API testing?

API authentication is a combination of technology or process that verifies the identities of users who want access to an API. It involves the use of software protocol to verify identity of the requester before granting access to protected resources.

API testing is a type of software testing that involves testing application programming interfaces (APIs) directly and as part of integration testing to determine if they meet expectations for functionality, reliability, performance, and security. Unlike UI testing, which focuses on the graphical interface of an application, API testing focuses on the business logic layer of the software architecture. With the increasing reliance on APIs in modern software architecture, mastering API testing has become indispensable for quality assurance professionals. Top companies like Google, Facebook, Amazon, Microsoft, and many others prioritize API testing to maintain their high standards of software quality.

In this article, we will provide Top API Testing Interview Questions tailored for both beginners and experienced professionals with 3, 5, and 8 years of experience. Here, we cover everything, including core API concepts, REST and SOAP protocols, testing tools, authentication methods, performance testing, error handling, and more, that will surely help you to crack API testing interviews.

The questions are divided into three categories:

• API Testing Interview Questions For Freshers
• API Testing Interview Questions For Intermediate
• API Testing Interview Questions For Experienced

The article also provides answers to each question, along with explanations and practical Example with PostMan. This will help you to understand the concepts behind the questions and to prepare for your interview.