API Testing Interview Questions - Part 1

 1. API - API is an application programming interface that acts as an intermediate between two applications. API is a collection of functions and procedures.

2. API Methods:

  GET - get requests are used to retrieve the information from the given URL.

  POST - To send the new data to an api.

  PUT - This method is used to update the existing data.

  DELETE - This is used to remove or delete the existing.

  PATCH - Partially updated resource.

3. What is the difference between 201 and 204 Status Code?

• 201 - The request was successful, and a new resource was created.
• 204 - The request was successful, but there is no response body. When an update or delete operation is successful.

4. What is the difference between 401 and 403 Status Code?

• 401 - Unauthorized. without logging in or with invalid credentials.
• 403 - Forbidden. When a logged-in user tries to access a restricted area without the required permissions.

5. What is the difference between Query Parameters and Path Parameters?

• Both Query Parameters and Path Parameters are used to send data in API requests.

6. How does an API Work?

• Client request -> Server Processing -> Response - Client Handling

7. Main types of API?

• Public API
• Private API
• Partner API
• Comboste API

8. What must be checked when performing API testing?

• Accuracy of data
• HTTP status codes
• Data type, validations, order, and completeness
• Authorization checks
• Implementation of response timeout
• Error codes in case the API returns, and

9. How do you handle dynamic data in API testing?

• Data Parameterization: Using data-driven tests where input values are generated dynamically from a data source (e.g., database, files).

10. What are the major challenges faced in API testing?

• Output verification and validation.

11. Difference b/w RESTful API and SOAP API?

• RESTful API and SOAP API lie in their architectural styles and message formats.

12. API Endpoint - Refers to a specific URL or URI

13. Purpose of authentication:

• Verify the requester identity before granting access to protected resources.

14. Authentication methods used in API Testing:

• Token-based authentication - A token to the client after successful authentication.
• Basic authentication - sending the username and password