API Assured API Testing Interview Questions

Introduction – Why API Testing Is Important in Interviews

With microservices, cloud platforms, and mobile applications dominating today’s software landscape, API testing has become a core skill for QA engineers and SDETs. That’s why interviewers frequently ask api assured api testing interview questions to evaluate whether candidates can validate backend logic, automate APIs, and ensure data integrity without relying on UI layers.

In particular, API Assured (Rest Assured) is widely used in Java-based automation frameworks. Interviewers test your understanding of:

• REST fundamentals
  
• HTTP methods and status codes
  
• API automation concepts
  
• Real-time debugging and validation scenarios
  

This article is designed for freshers to experienced professionals, covering theory + practical examples + scenario-based questions in a simple, interview-focused manner.

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What Is API Testing? (Clear & Simple)

API testing is the process of validating Application Programming Interfaces directly by sending requests and verifying responses for correctness, performance, security, and reliability assume correct behavior of the system.

In short:

API testing ensures the application works correctly at the service and data layer.

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REST vs SOAP vs GraphQL

Feature	REST	SOAP	GraphQL
Type	Architectural style	Protocol	Query language
Data format	JSON	XML	JSON
Performance	Fast & lightweight	Slower	Highly optimized
Flexibility	High	Low	Very high
Usage	Most modern apps	Legacy/enterprise	Modern frontend-driven apps

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70+ API Assured API Testing Interview Questions and Answers

Basic API & Rest Assured Questions (Freshers)

1. What is API Assured (Rest Assured)?
   API Assured, commonly known as Rest Assured, is a Java-based library used for automating REST API testing.
   
2. Why use Rest Assured for API testing?
   It simplifies API automation by providing readable syntax for request and response validation.
   
3. Which language is used in API Assured?
   Java.
   
4. What are the main HTTP methods?
   GET, POST, PUT, PATCH, DELETE.
   
5. What is an endpoint?
   The URL that receives API requests.
   
6. What is a request payload?
   Data sent to the server in POST/PUT requests.
   
7. What is a response payload?
   Data returned by the server.
   
8. What is statelessness in REST?
   Each request is independent; no session data stored on the server.
   
9. What is idempotency?
   Multiple identical requests produce the same result.
   
10. What is the base URI in Rest Assured?
    The root URL of the API being tested.
    

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REST API Interview Questions

11. Difference between POST and PUT?
    POST creates a new resource; PUT updates or replaces an existing one.
    
12. What is JSON?
    A lightweight data format used for REST APIs.
    

{

  “id”: 101,

  “name”: “Srushti”,

  “role”: “QA Engineer”

}

13. What are headers in API testing?
    Metadata such as Content-Type and Authorization.
    
14. What is Content-Type?
    Specifies the format of request/response (application/json).
    
15. What is API versioning?
    Managing changes using /v1, /v2, or headers.
    
16. What is query parameter?
    Parameters passed after ? in the URL.
    
17. What is path parameter?
    Dynamic values inside the endpoint path.
    
18. What is pagination?
    Splitting large data into pages.
    
19. What is caching?
    Storing responses to reduce server load.
    
20. What is HATEOAS?
    REST principle where responses include navigation links.
    

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SOAP & XML Questions

21. What is SOAP?
    A protocol for exchanging structured XML messages.
    
22. What is WSDL?
    An XML document describing SOAP services.
    
23. What is SOAP Envelope?
    The root XML element in SOAP.
    
24. How do you validate XML response?
    Using XPath.
    

<response>

  <status>SUCCESS</status>

</response>

25. SOAP vs REST – which is better?
    REST is simpler and faster; SOAP is more secure and structured.
    

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Status Codes – Interview Essentials

Code	Meaning
200	OK
201	Created
204	No Content
400	Bad Request
401	Unauthorized
403	Forbidden
404	Not Found
409	Conflict
500	Internal Server Error

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API Validation Example (Real-Time)

Request

POST /api/users

Payload

{

  “email”: “test@example.com”,

  “password”: “Test@123”

}

Response

{

  “id”: 501,

  “message”: “User created successfully”

}

Validations

• Status code = 201
  
• id should not be null
  
• message equals expected text
  

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Automation Snippets (Mandatory for Interviews)

Rest Assured (Java – API Assured)

given()

  .baseUri(“https://api.test.com”)

  .header(“Content-Type”,”application/json”)

.when()

  .get(“/users/101”)

.then()

  .statusCode(200)

  .body(“name”, equalTo(“Srushti”));

Postman (Manual Testing)

• Validate status code
  
• Verify response body
  
• Use environment variables
  

SoapUI Assertions

• JSONPath Match
  
• XPath Match
  
• Schema Compliance
  

Python (Requests Library)

import requests

res = requests.get(“https://api.test.com/users/101”)

assert res.status_code == 200

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Scenario-Based REST API Testing Questions (10+)

31. API returns 200 but incorrect data. What do you do?
    Validate business logic and raise a functional defect.
    
32. How do you test token expiration?
    Use expired token and validate 401 response.
    
33. How do you test rate limiting?
    Send multiple rapid requests and expect 429.
    
34. How do you test negative scenarios?
    Invalid payloads, missing headers, wrong data types.
    
35. How do you test API performance?
    Measure response time and SLA.
    
36. How do you test file upload API?
    Validate size, format, and response message.
    
37. How do you test dependent APIs?
    Chain requests and validate output.
    
38. What if backend is unavailable?
    Use mock services.
    
39. How do you test concurrency?
    Parallel requests and data consistency checks.
    
40. How do you test backward compatibility?
    Validate older API versions.
    

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How Interviewers Evaluate Your Answers

Interviewers assess:

• Core understanding of API concepts
  
• Knowledge of Rest Assured syntax
  
• Usage of status codes
  
• Ability to explain real-time scenarios
  
• Logical debugging approach
  

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API Assured API Testing Cheat Sheet

• Validate status + body
  
• Cover positive and negative cases
  
• Parameterize test data
  
• Handle authentication dynamically
  
• Use assertions effectively
  
• Log defects with request/response
  

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FAQs – API Assured API Testing

Q1. Is API Assured same as Rest Assured?
Yes, API Assured usually refers to Rest Assured.

Q2. Is API automation mandatory for testers?
Not mandatory, but highly preferred.

Q3. Can freshers learn API Assured?
Yes, basics are easy to start.

Q4. Is Postman enough for interviews?
Manual knowledge is good; automation gives an edge.