SoapUI API Testing Interview Questions

Introduction – Why API Testing Matters in Interviews

In modern application architectures (microservices, mobile apps, cloud systems), APIs are the backbone. Interviewers ask soapui api testing interview questions to evaluate how well you understand backend validation, data integrity, security, and automation—beyond UI testing. Strong API knowledge shows you can test systems early, find defects faster, and collaborate effectively with developers.

This guide is built for freshers to experienced QA/API testers, with real-time examples, status codes, JSON/XML samples, and scenario-based REST API testing questions you’ll face in technical rounds.

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What is API Testing? (Simple & Clear)

API testing validates application programming interfaces directly to ensure they return correct data, proper status codes, secure responses, and expected behavior under various conditions—without relying on UI.

Key benefits:

• Faster feedback than UI testing
  
• Stable tests (UI changes don’t break APIs)
  
• Early bug detection
  
• Ideal for automation
  

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REST vs SOAP vs GraphQL (Quick Comparison)

Feature	REST	SOAP	GraphQL
Protocol	Architectural style	Protocol	Query language
Data format	JSON (mostly)	XML only	JSON
Performance	Lightweight, fast	Heavy	Efficient, flexible
Caching	Yes	Limited	Client-controlled
Tooling	SoapUI, Postman, RestAssured	SoapUI	Postman, Apollo

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50+ SoapUI API Testing Interview Questions & Answers

Basics (Freshers)

1. What is SoapUI?
   SoapUI is an API testing tool (by SmartBear) used to test REST and SOAP services using functional, security, and load tests.
   
2. Why use SoapUI for API testing?
   Supports REST/SOAP, assertions, data-driven testing, scripting (Groovy), and mock services.
   
3. What is an endpoint?
   A specific URL where an API resource is accessible.
   
4. What is a resource in REST?
   An object/data (e.g., /users, /orders/123).
   
5. HTTP methods supported?
   GET, POST, PUT, PATCH, DELETE, OPTIONS, HEAD.
   
6. What is WSDL?
   Web Services Description Language—XML describing SOAP services.
   
7. Difference between PUT and PATCH?
   PUT replaces the resource; PATCH partially updates it.
   
8. What is payload?
   The request/response body (JSON/XML).
   
9. What is a header?
   Metadata like Content-Type, Authorization.
   
10. What is authentication vs authorization?
    AuthN verifies identity; AuthZ checks permissions.
    

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SoapUI Features & Assertions

11. What are assertions in SoapUI?
    Checks that validate responses (status code, content, schema).
    
12. Common assertions you used?
    Valid HTTP Status Codes, Contains, XPath/JSONPath Match, Schema Compliance.
    
13. How to validate JSON response in SoapUI?
    Use JSONPath assertions.
    

{

  “id”: 101,

  “name”: “Srushti”,

  “role”: “QA”

}

JSONPath: $.name → Expected: Srushti

14. How to validate XML response?
    Use XPath assertions.
    
15. What is a TestSuite/TestCase/TestStep?
    Hierarchy: Project → TestSuite → TestCase → TestSteps.
    
16. What scripting language does SoapUI use?
    Groovy.
    
17. How to parameterize requests?
    Using properties (Project/TestSuite/TestCase).
    
18. What is a Mock Service?
    Simulates API behavior when backend isn’t ready.
    

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REST API Interview Questions

19. What is idempotency?
    Multiple identical requests yield the same result (GET, PUT).
    
20. What is statelessness?
    Server doesn’t store client session state.
    
21. How do you test pagination?
    Validate page, size, total counts.
    
22. How to test filtering/sorting?
    Verify query params affect response correctly.
    
23. How to test API versioning?
    /v1/users vs /v2/users behavior checks.
    

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Status Codes (Must-Know)

24. 200 OK – Successful request
    
25. 201 Created – Resource created
    
26. 204 No Content – Success without body
    
27. 400 Bad Request – Validation error
    
28. 401 Unauthorized – Missing/invalid auth
    
29. 403 Forbidden – No permission
    
30. 404 Not Found – Resource missing
    
31. 409 Conflict – Duplicate/constraint issue
    
32. 500 Internal Server Error – Server failure
    

SoapUI Assertion:
Valid HTTP Status Codes → Expected: 200

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Real-Time API Validation Example

Request

POST /api/users

Content-Type: application/json

Payload

{

  “email”: “test@example.com”,

  “password”: “Pass@123”

}

Expected Response

{

  “id”: 555,

  “message”: “User created successfully”

}

Assertions

• Status code = 201
  
• $.id exists
  
• $.message equals expected text
  

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Automation & Tooling

33. How is SoapUI different from Postman?
    SoapUI is stronger in assertions, mocks, load tests; Postman excels in collaboration and simplicity.
    
34. What is RestAssured?
    Java library for API automation.
    

given()

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

 .when()

 .get(“/users/1”)

 .then()

 .statusCode(200);

35. Can we automate APIs with Python?
    

import requests

r = requests.get(“https://api.example.com/users/1”)

assert r.status_code == 200

36. How to handle OAuth2 in SoapUI?
    Configure OAuth profile and attach token.
    
37. How to test negative scenarios?
    Invalid inputs, missing headers, wrong auth.
    

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Scenario-Based REST API Testing Questions (10+)

38. API returns 200 but wrong data—what do you do?
    Validate schema, business rules, and log a functional defect.
    
39. How do you test rate limiting?
    Send multiple rapid requests; expect 429.
    
40. How do you test file upload API?
    Validate file type, size limits, success response.
    
41. Token expires mid-test—solution?
    Auto-refresh token via script.
    
42. API depends on another service—how test?
    Use mock services.
    
43. How test concurrency?
    Parallel requests; verify no data corruption.
    
44. Response time is slow—what check?
    Measure latency; validate SLAs.
    
45. How test data consistency across APIs?
    Chain requests and compare responses.
    
46. How validate error messages?
    Exact text, error codes, localization.
    
47. How test backward compatibility?
    Validate older clients still work with new versions.
    

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How Interviewers Evaluate Your Answers

Interviewers look for:

• Clear API fundamentals
  
• Real-time examples
  
• Knowledge of status codes
  
• Hands-on assertions & automation
  
• Problem-solving in scenarios
  

Tip: Explain why you test something, not just how.

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SoapUI API Testing Cheat Sheet (Revision)

• Use JSONPath/XPath assertions
  
• Always validate status + body
  
• Cover positive & negative cases
  
• Parameterize data
  
• Handle auth tokens dynamically
  
• Log meaningful defects with request/response
  

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FAQs (For Google Ranking)

Q1. Is SoapUI good for REST API testing?
Yes, it supports REST with strong assertions and scripting.

Q2. Do interviewers ask SoapUI scripting questions?
Yes, basic Groovy scripting is common for experienced roles.

Q3. Can freshers crack API interviews?
Yes—focus on basics, status codes, and simple scenarios.

Q4. Is Postman required along with SoapUI?
Knowing both helps; SoapUI depth + Postman usability is ideal.