Interview Questions

1. What is an API?

A.  An API, or Application Programming Interface, is a set of rules and protocols that allows different software applications to communicate with each other. APIs define the methods and data formats that applications can use to request and exchange information, enabling them to interact in a standardized way.

2. What is API testing?

A. API testing is the process of verifying and validating the functionality, reliability, performance, and security of an Application Programming Interface (API). It focuses on ensuring that the API meets the expected requirements and performs its intended tasks accurately and efficiently.

3. Why is API testing important?

A. API testing is important because it ensures the integrity, reliability, and performance of the software components that rely on APIs. Here are some key reasons why API testing is crucial,

4. Could you explain the differences between API testing and UI testing?

API Testing:

  • Focus: Tests the application’s business logic, data handling, and response without involving the user interface.
  • Scope: Directly tests the API endpoints and their interactions, ensuring that the underlying logic and data processing work as intended.

UI Testing:

  • Focus: Tests the user interface to ensure that the application looks and behaves correctly from the end-user’s perspective.
  • Scope: Involves testing graphical user interface elements like buttons, menus, forms, and overall layout to verify that they function correctly and provide a good user experience.

5. What are the common types of API protocols?

A. REST (Representational State Transfer)
  • Characteristics: REST APIs use standard HTTP methods (GET, POST, PUT, DELETE) and follow a stateless, client-server architecture.
  • Data Format: Typically JSON or XML.
  • Use Cases: Web services, cloud applications, mobile apps.

6. What tools do you use for API testing?

  •  The tool that is most commonly used for API testing is Testim. Testim is a powerful tool for API testing that makes it easy to create and execute automated tests for your API.

7. How do you validate the response of an API?

  • validate an API response, inspect HTTP status codes, check response headers and content, verify data accuracy against expected values, assess performance metrics, and employ assertions or validation libraries for comprehensive testing

8. What is the purpose of API documentation?

  •  Guidance for Developers: It helps developers understand how to effectively use the API. This includes explaining the available endpoints, the parameters required, the responses, error codes, and the overall functionality.
  •  Ease of Integration: Good documentation makes it easier for developers to integrate the API into their applications. It provides examples, use cases, and detailed descriptions that can help avoid common pitfalls and reduce the time spent on troubleshooting.

9. What are the main differences between REST and SOAP APIs?

  • REST APIs lack a standardized messaging system and mainly handle communication failures by retrying various requests. On the other hand, SOAP APIs have built-in retry logic, allowing them to handle errors more effectively and provide better reliability. SOAP supports ACID compliance

10. What is JSON and why is it commonly used in APIs?

  • JSON (JavaScript Object Notation) is commonly used for data storage and transfer. JSON is a popular choice for applications that benefit from a simple and easy-to-use data format. XML (Extensible Markup Language) is a general-purpose markup language similar to JSON that allows for more complex data structures

11. What is an endpoint in an API?

  • A. In the context of an API (Application Programming Interface), an endpoint refers to a specific URL (Uniform Resource Locator) or URI (Uniform Resource Identifier) that is used to access a particular resource or functionality provided by the API.

12. What is a request and a response in the context of an API?

  • An API request and response are the two fundamental components of communication between a client application and a server application via an API(Application Programming Interface). An API request is a message sent by a client application to a server application through an API, requesting information or action

13. What are HTTP methods? Name a few.

  • The primary or most commonly used HTTP methods are POST, GET, PUT, PATCH, and DELETE. These methods correspond to create, read, update, and delete (or CRUD) operations, respectively. There are a number of other methods, too, but they are utilized less frequently.
  1. What is the difference between PUT and POST methods?
  • Purpose: The PUT method is primarily used to update or replace an existing resource or collection of resources on the server. It expects the client to provide the full representation of the resource(s) with the updated information.
  • Idempotent: PUT requests are idempotent, meaning that multiple identical requests should have the same effect as a single request. If a resource already exists at the specified URI, PUT will update it. If it does not exist, PUT may create it, depending on the server implementation.
  • Example: Updating a user’s profile information where the entire updated user object is sent in the request body to replace the existing user object on the server.

15. How do you handle authentication in API testing?

  •  In the case of REST API, authentication takes place by using HTTP requests. The process of authentication is not complicated. A REST request can carry a special header which can be named Authorization header.

16. What is OAuth and how is it used in API security?

  • OAuth (short for Open Authorization) is a popular, standardized API protocol that provides a secure way for services to quickly share resources for a seamless user experience.

17. What is a status code in an API response? Provide examples.

  •  HTTP status codes are three-digit codes that indicate the outcome of an API request. They are included in the API’s response to the API client, and they include important information that helps the client know how to proceed

18. How do you handle error responses in API testing?

  • Handling error responses in API testing is crucial to ensure that the API behaves correctly under various error conditions. Here are steps and best practices to handle error responses in API testing:
  • Identify Possible Error Scenarios:
    • Invalid request parameters
    • Missing authentication or authorization
    • Resource not found
    • Rate limiting or throttling
    • Server errors (e.g., 500 Internal Server Error)
  • Set Up Test Cases for Each Error Scenario:
  • Design tests that trigger each type of error response.
      • Use different combinations of invalid inputs, such as incorrect data types, missing required fields, or invalid values.

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