API Testing Interview Questions for Freshers

Introduction – Why API Testing Is Important in Interviews

 For freshers entering the software testing field, API testing has become a must-have skill. Even entry-level QA roles now expect candidates to understand how applications work beyond the UI. 

Interviewers ask api testing interview questions for freshers to check whether you: 

  • Understand how frontend and backend communicate  
  • Know basic REST API concepts  
  • Can validate responses and status codes  
  • Are familiar with tools like Postman or SoapUI  
  • Can think logically about real-world scenarios  

The Good News for Freshers 

You do not need deep automation, coding, or performance testing expertise as a fresher. 

Most companies mainly look for: 

  • Strong fundamentals  
  • Clear explanations  
  • Basic hands-on practice  
  • Logical thinking  
  • Confidence during interviews  

If you understand: 

  • How APIs work  
  • Basic HTTP methods  
  • Status codes  
  • Request and response validation  
  • Simple API scenarios  

then you are already well prepared for many fresher QA interviews. 

Why API Testing is Important Today 

Modern applications rely heavily on APIs for communication between: 

  • Frontend and backend systems  
  • Mobile apps and servers  
  • Third-party integrations  
  • Cloud services  
  • Payment gateways  

Because APIs handle critical application functionality, companies expect testers to validate backend behavior instead of checking only the UI. 

What Is API Testing? (Clear & Simple)  

API testing is a type of software testing that validates the functionality, reliability, performance, and security of APIs (Application Programming Interfaces) by sending requests and verifying responses. 

Instead of testing the graphical user interface (UI), API testing focuses on backend communication between systems. APIs act as intermediaries that allow different software applications to exchange data and communicate with each other. 

API testing verifies whether APIs: 

  • Return correct responses  
  • Process requests accurately  
  • Handle errors properly  
  • Maintain security standards  
  • Perform efficiently under load conditions  

Why API Testing Is Important 

Modern applications depend heavily on APIs for communication between: 

  • Web applications  
  • Mobile applications  
  • Databases  
  • Third-party services  
  • Cloud platforms  

If APIs fail, important business operations may stop functioning properly. 

Areas Validated in API Testing 

Functional Validation 

Checks whether APIs work according to business requirements. 

Data Validation 

Ensures API responses contain accurate data. 

Error Handling 

Validates how APIs behave under invalid conditions. 

Security Validation 

Checks authentication and authorization mechanisms. 

Performance Validation 

Measures response time and scalability. 

Example 

Sending a GET request to: 

/users/1 

and validating whether the correct user details are returned in the response. 

Real-Time Scenario 

In a banking application, API testing verifies whether account balance APIs return accurate balance information after successful authentication. 
 

REST vs SOAP vs GraphQL (Beginner-Level Comparison) 

Feature REST SOAP GraphQL 
Protocol HTTP XML-based HTTP 
Data Format JSON / XML XML only JSON 
Complexity Easy Moderate Moderate 
Usage Most modern apps Banking / legacy Modern apps 

 For freshers, REST API basics are most important. SOAP knowledge is a plus. 

API Testing Interview Questions for Freshers (90+ Questions with Answers) 

Section 1: Basic API Concepts (Q1–Q20) 1. What is an API? 

An API (Application Programming Interface) is a mechanism that allows two software applications to communicate and exchange data with each other. APIs act as intermediaries between systems so that one application can request services or data from another application without knowing its internal implementation. 

For example, when a mobile banking app shows your account balance, the app sends a request to the bank server through an API. The server processes the request and sends the response back to the application. 

APIs are widely used in: 

  • Mobile applications  
  • Web applications  
  • Payment gateways  
  • Social media integrations  
  • Cloud services  

Without APIs, modern software systems would not be able to interact efficiently. 

2. What is API testing? 

API testing is a type of software testing that verifies whether APIs are working correctly according to business and technical requirements. Instead of testing the user interface, API testing focuses on backend communication between systems. 

In API testing, testers validate: 

  • Requests  
  • Responses  
  • Status codes  
  • Headers  
  • Authentication  
  • Business logic  
  • Data accuracy  
  • Error handling  

For example, when testing a login API, testers check whether valid credentials return a success response and invalid credentials return proper error messages. 

API testing is important because APIs connect different modules and services inside applications. 

3. Why is API testing important? 

API testing is important because APIs are the backbone of modern applications. If APIs fail, multiple systems and functionalities can stop working properly. 

Key reasons why API testing is important: 

  • APIs connect frontend and backend systems  
  • APIs are used across mobile, web, and third-party systems  
  • Backend failures directly impact users  
  • API defects are easier to detect early than UI defects  
  • APIs handle critical business data  

For example, if a payment API fails in an e-commerce application, customers cannot complete purchases. 

API testing also improves: 

  • Application reliability  
  • Security  
  • Performance  
  • Integration quality  

4. API testing vs UI testing? 

API testing and UI testing differ mainly in the layer they validate. 

API Testing 

API testing checks backend functionality directly by sending requests to APIs and validating responses. 

It focuses on: 

  • Business logic  
  • Data processing  
  • Response validation  
  • Performance  
  • Security  

UI Testing 

UI testing validates the frontend user interface and user interactions. 

It focuses on: 

  • Buttons  
  • Forms  
  • Navigation  
  • Layout  
  • User experience  

Key Difference 

API testing validates how systems work internally, while UI testing validates how applications behave visually for users. 

API testing is usually: 

  • Faster  
  • More stable  
  • Easier to automate  
  • Better for early defect detection  

5. What types of APIs are commonly tested? 

The two most tested APIs are: 

REST APIs 

REST (Representational State Transfer) APIs use HTTP methods and mostly exchange data in JSON format. 

Features: 

  • Lightweight  
  • Fast  
  • Widely used  
  • Easy to integrate  

SOAP APIs 

SOAP (Simple Object Access Protocol) APIs use XML-based messaging. 

Features: 

  • Highly structured  
  • More secure in enterprise environments  
  • Common in banking and legacy systems  

REST APIs are more popular in modern applications, while SOAP APIs are still used in enterprise systems. 

6. What is REST? 

REST stands for Representational State Transfer. It is a lightweight architectural style used to build web services and APIs. 

REST APIs use: 

  • HTTP methods  
  • URLs  
  • Stateless communication  
  • JSON data format  

Common HTTP methods in REST: 

  • GET  
  • POST  
  • PUT  
  • DELETE  
  • PATCH  

REST APIs are popular because they are: 

  • Simple  
  • Fast  
  • Scalable  
  • Easy to consume  

Example: 

GET /users/101 

This request retrieves details of user 101. 

7. What is SOAP? 

SOAP stands for Simple Object Access Protocol. It is a protocol used for exchanging structured information between systems using XML. 

SOAP APIs: 

  • Use XML format  
  • Follow strict standards  
  • Support advanced security  
  • Work well in enterprise applications  

SOAP messages contain: 

  • Envelope  
  • Header  
  • Body  

SOAP is commonly used in: 

  • Banking systems  
  • Insurance applications  
  • Enterprise software  

Although SOAP is more secure and standardized, it is heavier and slower than REST. 

8. What is an endpoint? 

An endpoint is a specific URL through which an API can be accessed. 

It represents a resource or service in the API. 

Example: 

/users/101 

This endpoint may return details of user 101. 

Endpoints are important because: 

  • They define where requests are sent  
  • They identify API resources  
  • They help applications communicate properly  

Different endpoints perform different operations. 

Examples: 

  • /users  
  • /orders  
  • /payments  

9. What is request payload? 

A request payload is the data sent from the client to the server inside the request body. 

It is mainly used in: 

  • POST requests  
  • PUT requests  
  • PATCH requests  

Example: 


 “name”: “Amit”, 
 “email”: “amit@test.com” 

This payload sends user information to the server. 

Testers validate: 

  • Required fields  
  • Data types  
  • Invalid inputs  
  • Missing values  

Payload validation is important for ensuring proper business functionality. 

10. What is response payload? 

A response payload is the data returned by the server after processing the API request. 

Example: 


 “id”: 101, 
 “name”: “Amit”, 
 “status”: “Active” 

The response payload helps clients understand whether the request succeeded or failed. 

Testers validate: 

  • Response values  
  • Response structure  
  • Data accuracy  
  • Error messages  

Response payload validation is one of the most important parts of API testing. 

11. What is statelessness? 

Statelessness means every API request is independent and self-contained. 

The server does not remember previous requests. 

Each request must include: 

  • Authentication details  
  • Required parameters  
  • Necessary headers  

Benefits of statelessness: 

  • Better scalability  
  • Simpler architecture  
  • Easier maintenance  
  • Improved reliability  

REST APIs are stateless by design. 

12. What is idempotency? 

Idempotency means performing the same API request multiple times produces the same result. 

Example: 

DELETE /users/101 

Deleting the same user repeatedly should still result in the user being deleted. 

Idempotent methods: 

  • GET  
  • PUT  
  • DELETE  

Non-idempotent method: 

  • POST  

Idempotency is important for: 

  • Reliability  
  • Retry mechanisms  
  • Preventing duplicate operations  

13. What is API versioning? 

API versioning is the practice of managing API changes without breaking existing applications. 

Versions are usually defined in URLs: 

/v1/users 
/v2/users 

Why versioning is important: 

  • Supports backward compatibility  
  • Allows safe feature updates  
  • Prevents application failures  

Without versioning, API changes can break client applications. 

14. What is authentication? 

Authentication is the process of verifying a user’s identity. 

It answers: 

“Who are you?” 

Examples: 

  • Username and password  
  • OTP verification  
  • API tokens  

Authentication ensures only valid users can access the system. 

15. What is authorization? 

Authorization is the process of checking what actions a user is allowed to perform. 

It answers: 

“What are you allowed to access?” 

Example: 

  • Admin users can delete records  
  • Normal users can only view records  

Authorization prevents unauthorized access to sensitive data. 

16. What authentication methods are common? 

Common authentication methods include: 

Basic Authentication 

Uses username and password. 

Bearer Token Authentication 

Uses tokens for secure API access. 

Example: 

Authorization: Bearer xyz123 

API Key Authentication 

Uses a unique API key provided by the server. 

These methods help secure APIs from unauthorized access. 

17. What is JSON? 

JSON (JavaScript Object Notation) is a lightweight data format used for data exchange in REST APIs. 

Example: 


 “id”: 101, 
 “name”: “Amit” 

Advantages: 

  • Easy to read  
  • Lightweight  
  • Faster processing  
  • Human-friendly  

JSON is the most widely used format in REST APIs. 

18. What is XML? 

XML (Extensible Markup Language) is a markup language used mainly in SOAP APIs. 

Example: 

<user> 
 <id>101</id> 
 <name>Amit</name> 
</user> 

Features: 

  • Structured format  
  • Self-descriptive  
  • Supports complex data  

XML is heavier than JSON but supports strict enterprise standards. 

19. What is negative testing? 

Negative testing checks how the API behaves with invalid inputs or unexpected conditions. 

Examples: 

  • Invalid credentials  
  • Missing fields  
  • Incorrect data types  
  • Unauthorized access  

Purpose: 

  • Ensure proper error handling  
  • Prevent crashes  
  • Improve application stability  

Negative testing is critical for identifying vulnerabilities and edge-case failures. 

20. What is positive testing? 

Positive testing verifies that APIs work correctly with valid inputs. 

Examples: 

  • Valid login credentials  
  • Correct request payloads  
  • Authorized access  

Purpose: 

  • Validate expected functionality  
  • Ensure successful responses  
  • Verify business logic  

Positive testing confirms the application works as intended. 

21. What validations are done in API testing? 

In API testing, multiple validations are performed to ensure the API behaves correctly and meets business requirements. 

Common validations include: 

  • Status code validation  
  • Response body validation  
  • Header validation  
  • Schema validation  
  • Response time validation  
  • Data validation  

For example, after creating a user through an API, testers verify: 

  • Status code is correct  
  • User details are returned properly  
  • Response format is valid  
  • API responds within expected time  

API validation ensures both technical correctness and business functionality. 

22. Is status code validation enough? 

No, validating only the status code is not enough in API testing. 

A status code may show success, but the response data may still contain incorrect or incomplete information. 

Example: 

  • API returns 200 OK  
  • But response contains wrong user data  

Testers must validate: 

  • Response body  
  • Business logic  
  • Headers  
  • Database changes  
  • Error messages  

Comprehensive validation ensures the API truly works as expected. 

23. What is header validation? 

Header validation means checking whether API headers contain correct information. 

Common headers: 

  • Content-Type  
  • Authorization  
  • Accept  
  • Cache-Control  

Example: 

Content-Type: application/json 

Header validation ensures: 

  • Proper data format  
  • Correct authentication  
  • Secure communication  

Incorrect headers can cause API failures or security issues. 

24. What is schema validation? 

Schema validation verifies whether the API response structure matches the expected format. 

It checks: 

  • Field names  
  • Data types  
  • Required fields  
  • JSON structure  

Example: 


 “id”: 101, 
 “name”: “Amit” 

If the API unexpectedly returns: 


 “userId”: “ABC” 

Schema validation fails because: 

  • Field name changed  
  • Data type is incorrect  

Schema validation helps maintain API consistency. 

25. What is response time testing? 

Response time testing measures how quickly an API responds to requests. 

Example: 

  • Login API should respond within 2 seconds  

Slow APIs negatively affect: 

  • User experience  
  • System performance  
  • Scalability  

Response time testing helps identify: 

  • Performance bottlenecks  
  • Server delays  
  • Heavy database operations  

Performance is critical for real-time applications. 

26. What is regression testing? 

Regression testing ensures that existing API functionality still works after code changes or new feature additions. 

Purpose: 

  • Detect unintended side effects  
  • Ensure stability after updates  

Example: 

  • New payment feature added  
  • Existing order APIs must still work correctly  

Regression testing is commonly automated to save time. 

27. What is smoke testing? 

Smoke testing is a basic health check performed to verify whether critical APIs are working. 

It is usually done: 

  • After deployments  
  • Before detailed testing  

Example: 

  • Verify login API works  
  • Verify main service endpoints respond  

Smoke testing helps quickly identify major failures. 

28. What is API security testing? 

API security testing checks whether APIs are protected from unauthorized access and vulnerabilities. 

It includes testing: 

  • Authentication  
  • Authorization  
  • Token validation  
  • Data exposure  
  • Injection attacks  

Example: 

  • Accessing admin APIs with normal user credentials  

Security testing is important because APIs often expose sensitive business data. 

29. What is API performance testing? 

API performance testing evaluates: 

  • Speed  
  • Stability  
  • Scalability  

It checks how APIs behave under: 

  • Heavy traffic  
  • Concurrent users  
  • Large data loads  

Goals: 

  • Prevent slowdowns  
  • Ensure reliability  
  • Handle high traffic efficiently  

Performance testing is critical for large-scale applications. 

30. What is pagination testing? 

Pagination testing verifies APIs that return data in multiple pages. 

Example: 

/users?page=1 

Pagination testing checks: 

  • Correct page size  
  • Accurate data count  
  • Navigation between pages  
  • Duplicate or missing records  

It is important for applications handling large datasets. 

31. What is filtering testing? 

Filtering testing verifies whether APIs correctly filter data based on query parameters. 

Example: 

/users?status=active 

Expected result: 

  • Only active users should be returned  

Filtering validation ensures: 

  • Accurate search results  
  • Correct business logic  

32. What is sorting testing? 

Sorting testing checks whether API responses are ordered correctly. 

Example: 

/products?sort=price 

Validation includes: 

  • Ascending order  
  • Descending order  
  • Alphabetical sorting  
  • Date sorting  

Sorting errors can affect user experience and reporting accuracy. 

33. What is API chaining? 

API chaining means using the response of one API as input for another API. 

Example: 

  1. Login API returns token  
  1. Token used in profile API  

API chaining simulates real user workflows and validates end-to-end functionality. 

34. What is API mocking? 

API mocking simulates API behavior without requiring the real backend service. 

Benefits: 

  • Faster testing  
  • Independent frontend development  
  • Early testing before backend completion  

Mock APIs return predefined responses for testing purposes. 

35. What is rate limiting? 

Rate limiting restricts the number of API requests allowed within a specific time period. 

Example: 

  • Maximum 100 requests per minute  

Purpose: 

  • Prevent abuse  
  • Protect servers  
  • Improve stability  

If limits are exceeded, APIs may return: 

429 Too Many Requests 

36. What is throttling? 

Throttling controls API traffic when request volume becomes too high. 

Unlike strict rate limiting, throttling may: 

  • Slow requests  
  • Delay responses  
  • Temporarily block excessive traffic  

Purpose: 

  • Maintain system stability  
  • Prevent server overload  

37. What is data consistency testing? 

Data consistency testing ensures the same data appears correctly across multiple systems and APIs. 

Example: 

  • User profile updated in one system  
  • Changes reflected in all connected systems  

It prevents: 

  • Data mismatches  
  • Synchronization issues  
  • Incorrect reporting  

38. What is API rollback testing? 

API rollback testing verifies that partial changes are not saved if an API operation fails. 

Example: 

  • Payment succeeds  
  • Order creation fails  

The system should rollback payment to maintain consistency. 

Rollback testing is important for: 

  • Financial systems  
  • Transaction processing  
  • Data integrity  

39. What is content-type validation? 

Content-type validation checks whether APIs send and receive data in the correct format. 

Common content types: 

  • application/json  
  • application/xml  

Example: 

Content-Type: application/json 

Incorrect content types may cause parsing failures or communication errors. 

40. What is boundary value testing? 

Boundary value testing checks API behavior using minimum and maximum input values. 

Examples: 

  • Minimum password length  
  • Maximum age value  
  • Numeric limits  

Boundary testing helps identify: 

  • Validation errors  
  • Overflow issues  
  • Edge-case failures  

41. What is concurrency testing? 

Concurrency testing verifies how APIs behave when multiple users access the system simultaneously. 

It helps detect: 

  • Data conflicts  
  • Race conditions  
  • Performance degradation  

Example: 

  • Multiple users booking the same ticket simultaneously  

Concurrency testing is important for scalable systems. 

42. What is API caching? 

API caching stores API responses temporarily to improve performance and reduce server load. 

Benefits: 

  • Faster response time  
  • Reduced database usage  
  • Better scalability  

Example: 

  • Frequently requested product data stored temporarily  

Caching improves application efficiency. 

43. What is API contract? 

An API contract is an agreement between client and server that defines: 

  • Request format  
  • Response structure  
  • Headers  
  • Authentication  
  • Error codes  

It ensures both systems communicate consistently. 

Breaking the API contract may cause application failures. 

44. What is API documentation? 

API documentation explains how APIs work and how developers should use them. 

It includes: 

  • Endpoints  
  • Request methods  
  • Parameters  
  • Sample requests  
  • Sample responses  
  • Authentication details  

Good documentation improves: 

  • Development speed  
  • Testing efficiency  
  • Integration accuracy  

45. What is OpenAPI/Swagger? 

OpenAPI (formerly Swagger) is a specification used to design, document, and test APIs. 

Swagger provides: 

  • Interactive API documentation  
  • API testing interface  
  • Request/response examples  

Benefits: 

  • Easy API understanding  
  • Faster integration  
  • Improved collaboration between teams  

Swagger is widely used in modern API development and testing. 

Real-Time API Validation Example (Fresher Level) 

Request 

POST /api/login 
 

 “username”: “testuser”, 
 “password”: “password123” 

Response 


 “token”: “abc123”, 
 “expiresIn”: 3600 

What to Validate in API Testing 

When testing this login API, freshers should understand that validation is not limited to checking only the status code. 

Important validations include: 

  • Status code should be 200  
  • Token should not be null or empty  
  • expiresIn value should be greater than 0  
  • Response format should be valid JSON  
  • Authentication token should be generated correctly  
  • API response time should be acceptable  

Why These Validations Matter 

Status Code Validation 

Confirms whether the API request succeeded. 

Token Validation 

Ensures authentication is working properly. 

expiresIn Validation 

Checks whether session expiry logic is correct. 

Response Validation 

Ensures the backend business logic is functioning properly. 

Postman / SoapUI / Automation Basics for Freshers 

Postman – Simple Test Script 

Example: 

pm.test(“Status code is 200”, function () { 
   pm.response.to.have.status(200); 
}); 

What This Script Does 

This script validates whether the API response status code is 200. 

Why Freshers Should Learn Postman 

Postman helps beginners: 

  • Send API requests  
  • Validate responses  
  • Practice real API scenarios  
  • Understand request-response flow  

It is one of the most commonly used tools in QA interviews. 

SoapUI – XPath Assertion 

Example: 

//token != “” 

What This Assertion Checks 

It verifies that the token value returned in the response is not empty. 

Why SoapUI is Used 

SoapUI is mainly used for: 

  • SOAP API testing  
  • XML response validation  
  • XPath assertions  

Freshers only need basic awareness initially. 

Rest Assured (Awareness) 

Rest Assured is a Java library used for API automation testing. 

Example: 

given() 
.when() 
.get(“/users/1”) 
.then() 
.statusCode(200); 

What This Code Does 

  • Sends a GET request  
  • Calls the /users/1 API  
  • Validates the response status code  

What Freshers Should Know 

As a fresher: 

  • Basic awareness is enough  
  • Understand that Rest Assured is used for API automation in Java  

You are usually not expected to build full automation frameworks initially. 

Python Requests (Awareness) 

Python provides a simple requests library for API testing. 

Example: 

import requests 
 
res = requests.get(url) 
 
assert res.status_code == 200 

What This Script Does 

  • Sends a GET request  
  • Stores API response  
  • Verifies the status code  

What Freshers Should Know 

You only need: 

  • Basic awareness  
  • Understanding that Python can also automate APIs  

Deep scripting knowledge is not mandatory for most fresher roles. 

Scenario-Based API Testing Interview Questions for Freshers 

1. API returns 200 but wrong data – what do you check? 

I would check: 

  • Response payload  
  • Database records  
  • Request parameters  
  • Backend business logic  

A 200 OK status does not guarantee correct data. 

2. API works in Postman but fails in application – why? 

Possible reasons: 

  • Incorrect frontend integration  
  • Missing headers  
  • Authentication mismatch  
  • Different environments  
  • CORS issues  

I would compare requests from both systems carefully. 

3. Missing parameter returns 500 – is it correct? 

Usually no. 

The API should ideally return: 

  • 400 Bad Request  

A 500 error indicates poor backend validation or unhandled exceptions. 

4. API allows access without token – what issue? 

This is a security issue. 

It indicates: 

  • Missing authentication  
  • Authorization bypass  
  • Improper API security validation  

5. Duplicate record created – what testing missed? 

Possible missing testing: 

  • Duplicate validation testing  
  • Idempotency testing  
  • Concurrency testing  

Proper validation should prevent duplicate records. 

6. API slow for large data – what test? 

This requires: 

  • Performance testing  
  • Load testing  
  • Scalability testing  

I would check: 

  • Response time  
  • Database performance  
  • Pagination support  

7. API returns null values – how validate? 

I would verify: 

  • Whether null values are expected  
  • Mandatory field handling  
  • Database records  
  • Backend mappings  

Unexpected null values may indicate data issues. 

8. Invalid input accepted – what defect? 

This is an input validation defect. 

Example: 

  • Invalid email accepted  
  • Negative values accepted  

Proper validations should reject invalid data. 

9. API returns wrong status code – impact? 

Wrong status codes can: 

  • Confuse frontend systems  
  • Break automation scripts  
  • Cause incorrect error handling  

Status codes must correctly represent API behavior. 

10. Same request gives different responses – why? 

Possible reasons: 

  • Dynamic backend data  
  • Caching issues  
  • Session dependency  
  • Concurrency problems  

I would investigate backend behavior and data consistency. 

11. Unauthorized user accesses data – issue? 

This is an authorization defect and a major security problem. 

Possible causes: 

  • Missing role validation  
  • Incorrect access control  
  • Broken permissions  

12. API fails only in production – possible reasons? 

Possible reasons: 

  • Environment differences  
  • Production database issues  
  • Server load  
  • SSL certificate issues  
  • Configuration mismatches  

Production problems are often environment-specific. 

How Interviewers Evaluate Freshers’ Answers 

Interviewers mainly focus on: 

  • Clarity of fundamentals  
  • Logical thinking  
  • Ability to explain practical examples  
  • Awareness of negative scenarios  
  • Confidence and communication  

Important Interview Tip 

Simple and clear answers usually score better than overly complicated technical jargon. 

Interviewers care more about: 

  • Understanding  
  • Practical thinking  
  • Problem-solving ability  

than memorized definitions. 

API Testing Interview Cheatsheet for Freshers 

Important Areas to Focus On 

  • Understand REST API basics  
  • Learn HTTP methods and status codes  
  • Validate response body, not only status codes  
  • Practice daily using Postman  
  • Think about negative testing scenarios  
  • Learn request and response validation  
  • Practice explaining concepts clearly  

Most Important Advice for Freshers 

Do not panic if you do not know automation yet. 

For many fresher QA interviews: 

  • Strong fundamentals  
  • Basic API knowledge  
  • Logical explanations  
  • Practical understanding  

matter more than advanced automation expertise. 

FAQs – API Testing Interview Questions for Freshers 

Q1. Is API testing mandatory for freshers? 
Yes, API testing has become very important for freshers in QA/testing roles, especially for manual testers and SDET roles. 

Most modern applications are built using APIs, so companies expect even entry-level testers to understand basic API concepts. 

Why API Testing is Important for Freshers 

APIs Power Modern Applications 

Today’s applications depend heavily on APIs for: 

  • Mobile apps  
  • Web applications  
  • Payment systems  
  • Login systems  
  • Third-party integrations  

Because of this, testers need to validate backend communication, not just UI behavior. 

Q2. Is Postman enough to start? 
Yes, Postman is usually enough for beginners and freshers to start learning API testing and clear many entry-level QA interviews. 

Why Postman is Enough for Beginners 

Postman helps freshers understand core API testing concepts without requiring programming knowledge. 

Using Postman, you can learn: 

  • Sending API requests  
  • HTTP methods (GET, POST, PUT, DELETE)  
  • Status code validation  
  • Request headers  
  • Authentication basics  
  • JSON request and response handling  
  • Negative testing scenarios  

This builds strong API fundamentals, which interviewers value most for fresher roles. 

Q3. Do freshers need automation skills? 
For freshers, automation knowledge is helpful but not always mandatory. It depends on the role and company. 

For Manual QA Fresher Roles 

Usually, basic manual testing + API testing knowledge is enough. 

Companies often expect: 

  • Manual testing concepts  
  • SDLC/STLC basics  
  • Bug reporting  
  • Basic SQL  
  • API testing with Postman  

In many beginner manual QA interviews, automation is considered an added advantage rather than a strict requirement. 

Q4. Biggest mistake freshers make? 
1. Memorizing Answers Without Understanding 

This is the biggest mistake. 

Many candidates memorize: 

  • Definitions  
  • Status codes  
  • Tool commands  

But during interviews, they struggle when interviewers ask: 

  • “Why?”  
  • “What if this fails?”  
  • “How would you test this scenario?”  

Interviewers care more about logical understanding than textbook definitions. 

Better Approach 

Understand: 

  • How APIs work  
  • Why validations matter  
  • What real defects look like  

2. Validating Only Status Codes 

Many beginners think: 

“200 means API is working.” 

That is incomplete testing. 

An API may return: 

  • Wrong data  
  • Missing fields  
  • Incorrect business logic  

while still returning 200 OK. 

Better Approach 

Always validate: 

  • Response body  
  • Business logic  
  • Headers  
  • Error messages  
  • Database impact (if possible)  

3. Ignoring Negative Testing 

Freshers often test only happy paths. 

Example: 

  • Valid login works  

But they forget to test: 

  • Invalid passwords  
  • Missing fields  
  • Empty payloads  
  • Unauthorized access  

Real bugs are often found in negative scenarios. 

Better Approach 

Always ask: 

“What happens if the user sends invalid data?” 

4. Focusing Only on UI Testing 

Some beginners test only frontend screens and ignore backend validation. 

Modern applications rely heavily on APIs, so backend understanding is very important. 

Better Approach 

Learn: 

  • API basics  
  • Request/response validation  
  • Postman basics  

Even simple API knowledge gives an advantage in interviews. 

5. Trying to Learn Too Many Tools Quickly 

Many freshers jump into: 

  • Selenium  
  • Automation frameworks  
  • Performance testing  
  • CI/CD  

without strong basics. 

This creates confusion and weak fundamentals. 

Better Approach 

Master basics first: 

  1. Manual testing  
  1. API testing fundamentals  
  1. SQL basics  
  1. One tool at a time  

6. Not Understanding Real-Time Scenarios 

Candidates often know definitions but cannot explain practical situations. 

Example interview question: 

“API returns 200 but wrong data—what will you do?” 

Many beginners struggle because they practiced theory only. 

Better Approach 

Practice: 

  • Scenario-based questions  
  • Real API validations  
  • Defect analysis thinking  

7. Fear of Automation 

Some freshers think: 

“I must know advanced automation immediately.” 

That is not true for most beginner roles. 

Better Approach 

Start small: 

  • Understand automation concepts  
  • Learn simple scripting gradually  
  • Build strong testing logic first  

8. Giving Very Complicated Answers 

Some candidates try to sound advanced and confuse themselves. 

Interviewers usually prefer: 

  • Clear explanations  
  • Simple language  
  • Logical thinking  

Better Approach 

Explain concepts simply with examples. 

Simple and correct answers are better than complicated and unclear answers. 

9. Not Practicing Hands-On Testing 

Watching tutorials alone is not enough. 

Many beginners never: 

  • Send real API requests  
  • Validate responses  
  • Test negative scenarios  

Better Approach 

Practice regularly using: 

  • Postman  
  • Public APIs  
  • Simple test cases  

Hands-on practice builds confidence quickly. 

10. Thinking Tools Are More Important Than Logic 

Tools change between companies. 

Testing fundamentals stay valuable everywhere. 

A candidate with strong: 

  • Testing mindset  
  • Validation logic  
  • Problem-solving ability  

often performs better than someone who only knows tool syntax. 

Q5. How to prepare in 1–2 weeks? 
Week 1 – Build Strong Fundamentals 

Day 1–2: Learn Manual Testing Basics 

Focus on: 

  • SDLC and STLC  
  • Bug life cycle  
  • Test case vs test scenario  
  • Severity vs priority  
  • Smoke testing  
  • Regression testing  

Goal 

You should be able to explain: 

  • What testing is  
  • Why testing is important  
  • How defects are identified  

Keep explanations simple. 

Day 3–4: Learn API Testing Basics 

Understand: 

  • What APIs are  
  • How frontend and backend communicate  
  • REST API basics  
  • SOAP basics (basic awareness only)  

Learn HTTP Methods 

  • GET – Retrieve data  
  • POST – Create data  
  • PUT – Update data  
  • DELETE – Remove data  

Learn Important Status Codes 

  • 200  
  • 201  
  • 400  
  • 401  
  • 404  
  • 500  

These are commonly asked in interviews. 

Day 5–6: Practice Using Postman 

This is the most important practical step. 

Practice: 

  • Sending GET requests  
  • Sending POST requests  
  • Adding headers  
  • Passing parameters  
  • Reading JSON responses  
  • Testing invalid inputs  

Learn Simple Validation 

Example: 

pm.response.to.have.status(200); 

Goal 

Become comfortable with: 

  • Request  
  • Response  
  • Headers  
  • JSON  
  • Status codes  

Day 7: Practice Scenario Questions 

Practice answering questions like: 

  • API returns wrong data  
  • Missing parameter returns 500  
  • Unauthorized access allowed  
  • API slow for large data  

Best Strategy 

Explain: 

  1. What you would check  
  1. Why the issue may happen  
  1. How you would validate it  

This improves logical thinking. 

Week 2 – Improve Confidence & Interview Readiness 

Day 8–9: Learn Basic SQL 

Focus only on beginner queries: 

SELECT * FROM users; 

Learn: 

  • SELECT  
  • WHERE  
  • ORDER BY  
  • JOIN basics  

Basic SQL knowledge is useful in many QA interviews. 

Day 10–11: Learn Automation Awareness 

You do not need advanced automation immediately. 

Just understand: 

  • What automation testing is  
  • Difference between manual and automation testing  
  • Basic awareness of:  
  • Selenium  
  • Rest Assured  

For freshers, awareness is usually enough. 

Day 12–13: Mock Interview Practice 

Practice: 

  • Speaking answers out loud  
  • Explaining APIs simply  
  • Giving practical examples  
  • Answering scenario questions confidently  

Important Tip 

Interviewers prefer: 

  • Clear explanations  
  • Logical thinking  
  • Confidence  

over complex jargon. 

Day 14: Revision Day 

Revise: 

  • HTTP methods  
  • Status codes  
  • API validations  
  • Postman basics  
  • Scenario questions  
  • Manual testing basics  

Avoid learning new topics on the last day. 

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