Top API Testing Interview Questions -

Introduction – Why API Testing Is Important in Interviews

APIs are the backbone of modern applications—connecting web applications, mobile apps, backend services, databases, and third-party systems. Because UI layers change frequently, interviewers often rely on API testing interview questions to evaluate whether candidates truly understand backend behavior, integrations, validations, and debugging approaches.

In interviews, recruiters usually assess whether you can:

Validate business logic without relying on UI

Understand REST and SOAP fundamentals

Verify status codes, headers, schemas, and authentication

Use tools like Postman, SoapUI, Rest Assured, and Python libraries

Explain real-time API issues and debugging strategies

This guide is suitable for:

Freshers

Manual QA engineers

API testers

Automation QA engineers

Experienced professionals

It includes:

Core API concepts

REST and SOAP basics

Real-time examples

Automation snippets

Scenario-based interview questions

Practical interview tips

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 (Interview Comparison)

Feature	REST	SOAP	GraphQL
Transport	HTTP	HTTP/SMTP	HTTP
Payload	JSON/XML	XML	JSON
Contract	Optional	WSDL	Schema
Performance	Fast	Slower	Optimized
Usage	Most modern apps	Banking/Legacy	Modern microservices

Top API Testing Interview Questions & Answers (100+)

Section A: Fundamentals (Q1–Q20)

What is an API?

An API is a contract that allows systems to communicate using requests and responses.

It enables applications such as web apps, mobile apps, databases, and third-party systems to exchange data and functionality.

What is API testing?

API testing validates:

Endpoints

Request payloads

Response payloads

Headers

Status codes

Authentication

Business rules

It ensures backend services work correctly without depending on UI.

API testing vs UI testing?

API Testing	UI Testing
Tests backend logic	Tests frontend presentation
Faster	Slower
Stable	UI-dependent
Validates integrations	Validates user workflows

API testing focuses on functionality and data flow, while UI testing focuses on user interaction.

HTTP methods?

Method	Purpose
GET	Retrieve data
POST	Create resource
PUT	Replace resource
PATCH	Partial update
DELETE	Remove resource

These methods are heavily used in REST APIs.

PUT vs PATCH?

PUT

Replaces the complete resource.

Example:
Updating all customer details.

PATCH

Updates only specific fields.

Example:
Updating only email address.

PATCH is more efficient for partial updates.

Endpoint?

An endpoint is a URL representing a resource or action.

Example:

/customers/101

Endpoints allow clients to interact with APIs.

Request payload?

Request payload is the data sent to the API in the request body.

Example:

{
“username”: “testuser”,
“password”: “pass123”
}

Commonly used in POST, PUT, and PATCH requests.

Response body?

Response body is the data returned by the API after processing the request.

Example:

{
“token”: “abc.def.xyz”,
“status”: “SUCCESS”
}

QA validates structure, values, and business rules.

Statelessness?

Statelessness means each request is independent.

The server does not automatically remember previous requests.

Every request must contain:

Authentication

Headers

Required data

REST APIs are generally stateless.

Idempotency?

Idempotency means repeated identical requests produce the same result.

Example:
Deleting the same resource multiple times should not create different outcomes.

Important for:

Retry handling

Distributed systems

Payment systems

Authentication vs Authorization?

Authentication	Authorization
Verifies identity	Verifies permissions
Who the user is	What the user can access

Example:

Admin access validates authorization

Common auth types?

Common authentication types:

Bearer Token

API Key

OAuth

Basic Authentication

These secure APIs from unauthorized access.

JWT?

JWT (JSON Web Token) is a signed token containing claims and user information.

JWT is commonly used for:

Authentication

Session handling

Secure API access

A JWT typically contains:

Header

Payload

Signature

API versioning?

API versioning manages changes without breaking existing consumers.

Example:

/api/v1/users
/api/v2/users

Benefits:

Backward compatibility

Controlled upgrades

Safer deployments

Schema?

Schema defines:

Structure

Data types

Mandatory fields

Validation rules

Examples:

JSON Schema

XSD Schema

Schema validation ensures API contracts remain consistent.

Negative testing?

Negative testing validates invalid scenarios.

Examples:

Invalid credentials

Missing headers

Expired token

Invalid payload

Unsupported methods

Purpose:
Ensure APIs fail gracefully.

Boundary testing?

Boundary testing validates minimum and maximum allowed values.

Example:
If quantity allowed is 1–100:

Test 0

Test 1

Test 100

Test 101

Helps identify edge-case defects.

Regression testing?

Regression testing re-validates APIs after:

Bug fixes

Enhancements

Deployments

Ensures existing functionality still works.

Smoke testing?

Smoke testing validates basic API health.

Checks:

APIs accessible

Core functionality working

Authentication functioning

Usually executed before detailed testing.

API chaining?

API chaining uses one API response in another request.

Example:

Token used in profile API

Profile ID used in order API

Simulates real business workflows.

Section B: Status Codes & Validations

Important HTTP Status Codes

Code	Meaning	Use
200	OK	Success
201	Created	Resource created
204	No Content	Success without response body
400	Bad Request	Invalid input
401	Unauthorized	Invalid authentication
403	Forbidden	No permission
404	Not Found	Invalid endpoint
409	Conflict	Duplicate resource
422	Unprocessable Entity	Business rule violation
500	Server Error	Backend failure

Is 200 enough?

No.

Even with status code 200:

Data may be incorrect

Business rules may fail

Null values may exist

Schema may change

Strong API testing validates both technical and business behavior.

Header validation?

Header validation checks:

Authorization

Content-Type

Cache-Control

Correlation IDs

Headers are critical for:

Authentication

Security

Caching

Integrations

Schema validation?

Schema validation ensures:

Correct response structure

Correct data types

Mandatory fields exist

This helps detect backend contract changes quickly.

Response time validation?

Response time validation ensures APIs meet SLA limits.

Example:
API should respond within:

2 seconds

5 seconds under load

Important for:

User experience

Performance

Scalability

Pagination testing?

Pagination testing validates:

Correct page size

Total record counts

Boundary pages

No duplicate records

Important for APIs returning large datasets.

Filtering/sorting?

Filtering validates query parameter behavior.

Example:

/users?status=active

Sorting validates response ordering:

Ascending

Descending

Ensures consistent API behavior.

Rate limiting?

Rate limiting restricts excessive API requests.

Example:
100 requests per minute.

After threshold, APIs may return:

429 Too Many Requests

Helps protect backend systems.

Caching?

Caching stores API responses temporarily for faster retrieval.

QA validates:

Cache headers

Expiration behavior

Data freshness

Important for performance optimization.

Concurrency?

Concurrency testing validates API behavior under simultaneous requests.

Checks:

Race conditions

Duplicate records

Data corruption

System stability

Very important in:

Banking systems

Ticket booking

E-commerce

Rollback?

Rollback ensures failed transactions do not partially save data.

Example:
Payment deducted but order creation failed.

Expected:
Entire transaction should rollback safely.

Data consistency?

Data consistency ensures same data appears correctly across:

APIs

Databases

External systems

Important for enterprise integrations.

Error messages?

Good API error messages should be:

Clear

Actionable

Consistent

Secure

Example:

{
“error”: “Invalid account ID”
}

Avoid exposing sensitive backend details.

Default values?

Default values are automatically applied when optional fields are omitted.

Example:
If currency not passed:

Default currency = USD

QA validates default behavior carefully.

Enums?

Enums restrict fields to predefined values.

Example:

“status”: [“ACTIVE”, “INACTIVE”, “BLOCKED”]

APIs should reject unsupported enum values.

Localization?

Localization testing validates language and regional behavior.

Checks:

Localized messages

Date formats

Currency formats

Language-specific responses

Example:
Different responses for:

English

French

Japanese

Important for global applications.

Section C: Functional Scenarios (Q36–Q60)

Test POST create?

Validate:

Status code = 201

Response body fields

Database side-effects

Resource creation

Business rules

Generated IDs

Audit/log entries

Example:
After creating an order:

orderId should exist

DB should contain new order

Inventory may reduce

Strong API testing validates both response and backend impact.

Test GET read?

Validate:

Status code = 200

Correct response fields

Filters

Sorting

Pagination

Data consistency

Example:

/users?status=active

Expected:
Only active users returned.

Test PUT/PATCH update?

Validate:

Updated fields changed correctly

Unchanged fields remain intact

Data consistency maintained

Correct timestamps updated

PUT

Replaces full resource.

PATCH

Updates only selected fields.

PATCH should not unexpectedly modify unrelated data.

Test DELETE?

Validate:

Status code = 204 or expected status

Resource removal

No orphan records

Correct authorization

Soft delete vs hard delete behavior

Example:
Deleted user should no longer appear in GET results.

Auth failures?

Validate:

401 for invalid/missing token

403 for insufficient permissions

Proper error messages

No unauthorized access

Security validation is critical in API testing.

Idempotency check?

Repeat the same PUT request multiple times.

Expected:

Same final outcome

No duplicate updates

No inconsistent state

Important in:

Payments

Distributed systems

Retry handling

Calculation rules?

Validate:

Totals

Discounts

Taxes

Currency precision

Rounding rules

Example:

total = subtotal – discount + tax

Financial APIs require strict calculation validation.

Date rules?

Validate:

Past/future constraints

Leap years

Expiration dates

Invalid date formats

Timezone handling

Example:
Past booking date should be rejected.

File upload APIs?

Validate:

File type restrictions

File size limits

Malware handling

Corrupted files

Empty files

Examples:

PDF only

Max 10MB upload

Webhooks?

Validate:

Trigger generation

Callback delivery

Retry behavior

Payload correctness

Authentication

Webhook testing ensures external integrations work correctly.

Dependencies?

Validate graceful failure handling when dependent systems fail.

Example:
Payment gateway unavailable.

Expected:

Proper error response

Retry handling

No partial transactions

Retries?

Validate behavior during transient failures.

Checks:

Duplicate prevention

Retry limits

Timeout handling

Exponential backoff

Critical in distributed systems.

Search APIs?

Validate:

Exact matches

Partial matches

Case sensitivity

Ranking behavior

Filters

Example:
Searching “John” should behave consistently.

Bulk operations?

Validate:

Multiple record processing

Partial success handling

Failure reporting

Transaction behavior

Example:
Bulk upload with one invalid record.

Expected:
Clear error handling.

Null handling?

Validate:

Required fields reject null

Optional fields accept null

Default values applied correctly

Null handling defects are common in APIs.

Backward compatibility?

Validate older clients continue working after API updates.

Example:
v1 clients should not break after v2 deployment.

Very important in enterprise systems.

ETags?

ETags support optimistic locking and caching.

Validate:

Concurrent update prevention

Version mismatch handling

Cache optimization

Common in REST APIs.

Sorting stability?

Validate deterministic ordering.

Example:
Repeated requests should return consistent sorted results.

Important for:

Pagination

Reporting

Search systems

Timezones?

Validate:

Correct timezone offsets

UTC conversion

Daylight savings behavior

Regional formatting

Timezone defects are common in global applications.

Precision/rounding?

Validate:

Decimal precision

Financial rounding

Currency calculations

Example:

19.999 → 20.00

Critical in banking and e-commerce systems.

Throttling headers?

Validate rate-limiting metadata.

Example headers:

X-RateLimit-Limit

X-RateLimit-Remaining

Ensure clients know remaining quota.

Cache invalidation?

Validate updates clear outdated cached data.

Example:
Updated product price should reflect immediately.

Cache-related defects can cause stale responses.

Soft delete?

Validate:

Resource hidden from normal queries

Data still exists internally

Restore functionality works

Different from hard deletion.

Feature flags?

Validate conditional behavior based on feature configuration.

Example:
New checkout flow enabled only for selected users.

Feature flags are common in modern deployments.

Observability?

Validate:

Trace IDs

Correlation IDs

Logging consistency

Monitoring visibility

Observability helps debug distributed systems effectively.

Status Codes + API Validation Example

Request

POST /api/orders

{
“productId”: 501,
“quantity”: 2,
“coupon”: “SAVE10”
}

Response

{
“orderId”: 9001,
“subtotal”: 200,
“discount”: 20,
“tax”: 18,
“total”: 198,
“status”: “CREATED”
}

Validations

Status code = 201

total = subtotal – discount + tax

quantity > 0

Fields exist

Correct data types

Order created successfully

Tooling & Automation Snippets

Postman Tests (JavaScript)

pm.test(“201 Created”, () => {

pm.response.to.have.status(201);

});

pm.test(“Total calculation”, () => {

const r = pm.response.json();

pm.expect(r.total).to.eql(r.subtotal – r.discount + r.tax);

});

Rest Assured (Java)

given()

.contentType(“application/json”)

.body(payload)

.when()

.post(“/orders”)

.then()

.statusCode(201)

.body(“status”, equalTo(“CREATED”));

Python Requests

import requests

res = requests.post(url, json=payload, headers=headers)

assert res.status_code == 201

data = res.json()

assert data[“total”] == data[“subtotal”] – data[“discount”] + data[“tax”]

Scenario-Based Practical API Testing Questions

200 OK but wrong total—what validations would you add?

Coupon applied twice—what business rule was missed?

Order created without authentication—what defect is this?

PATCH updates all fields—what issue does this indicate?

DELETE returns 200 with body—is it acceptable?

Pagination returns duplicates—possible causes?

Overselling stock—how would you test concurrency?

Expired token still works—what security defect is this?

422 vs 400—when should each be used?

Non-deterministic responses—possible reasons?

Timezone bugs—how would you identify them?

Search ignores filters—where would you investigate?

Retry creates duplicates—how would you prevent this?

Webhook not triggered—how would you verify?

Schema changed silently—what impact could occur?

How Interviewers Evaluate Your Answers

Interviewers usually look for:

Clear functional reasoning

Validation beyond status codes

Real-world examples

Edge-case awareness

Tool usage and assertions

Calm debugging approach

Strong candidates explain:

What they validate

Why they validate it

Expected business impact

API Testing Interview Cheatsheet

Validate business rules carefully

Test positive and negative scenarios

Never trust only HTTP 200

Validate schema and headers

Handle edge cases

Test security properly

Use automation where possible

Think about backend impact and data consistency

FAQs – Top API Testing Interview Questions

Q1. Is Postman enough?
Yes — for many QA and API testing interviews, Postman is enough to clear interviews, especially for:

Fresher QA roles

Manual QA roles

API Tester positions

Mid-level functional testing roles

But it depends on the company and role expectations.

When Postman Is Usually Enough

1. Manual QA Interviews

Interviewers mainly expect:

API fundamentals

REST basics

Status codes

Authentication

Request/response validation

Negative testing

Basic automation scripts

Postman covers all of these very well.

2. REST API Testing Projects

Most modern applications use REST APIs and JSON.

Postman is excellent for:

Sending requests

Testing endpoints

Validating responses

Authentication testing

Collection execution

Environment variables

For many SaaS and startup companies, Postman knowledge is often sufficient.

3. Beginner API Automation

Postman supports:

JavaScript assertions

Collection runners

Environment management

Newman CLI

Example:

pm.test(“Status code is 200”, function () {

pm.response.to.have.status(200);

});

Basic automation awareness through Postman is enough for many interviews.

Q2. REST or SOAP?
Neither REST nor SOAP is universally “better.”
They are designed for different use cases.

In modern applications, REST is more common.
In enterprise systems, SOAP is still heavily used.

What is REST?

REST (Representational State Transfer) is a lightweight architectural style used for APIs.

REST APIs usually:

Use JSON

Use HTTP methods

Are fast and simple

Are easy to integrate

Example REST request:

{
“username”: “testuser”,
“password”: “pass123”
}

REST is widely used in:

Mobile apps

Web applications

SaaS products

Microservices

What is SOAP?

SOAP (Simple Object Access Protocol) is an XML-based messaging protocol.

SOAP APIs:

Use XML

Follow strict standards

Use WSDL contracts

Support enterprise security

Example SOAP request:

<soapenv:Envelope>
  <soapenv:Body>
     <getBalance>
        <accountId>101</accountId>
     </getBalance>
  </soapenv:Body>
</soapenv:Envelope>

SOAP is common in:

Banking

Insurance

Telecom

Healthcare

Government systems

Q3. Biggest mistake?
The biggest mistake candidates make in API testing interviews is focusing only on tools and status codes instead of understanding real business behavior and backend validation.

Many candidates think:

“I sent the request in Postman and got 200 OK, so the API works.”

But interviewers expect much deeper analysis, especially for candidates with around 2 years of experience.

1. Trusting Only 200 OK

This is the most common mistake.

Candidates often validate only:

Status code = 200

But APIs can still return incorrect business data.

Example

{
“total”: -500
}

The API technically succeeded, but the business logic is wrong.

Interviewers expect validation of:

Response body

Business calculations

Database updates

Schema

Headers

Workflow behavior

Not just status codes.

2. Knowing Only Basic Postman Usage

Many candidates only know:

Sending requests

Checking response

Viewing status code

But at 2 years experience, interviewers expect more advanced usage such as:

Assertions

API chaining

Dynamic variables

Pre-request scripts

Environment variables

Collection Runner

Negative testing

Example

pm.expect(r.total).to.eql(r.subtotal – r.discount + r.tax);

This demonstrates business validation thinking.

3. Ignoring Business Logic

API testing is not only technical testing.

Interviewers expect candidates to validate:

Discounts

Tax calculations

Order workflows

Payment handling

Access permissions

Duplicate prevention

Example Questions

Can duplicate orders happen?

Can unauthorized users access APIs?

Are invalid transactions blocked?

Does rollback work properly?

Business logic validation is one of the most important interview areas.

4. No Negative Testing Mindset

Many candidates test only happy paths.

Strong candidates always test:

Invalid payloads

Missing fields

Expired tokens

Invalid authentication

Boundary values

Special characters

Empty requests

Negative testing shows deeper understanding of API behavior.

5. Weak Debugging Approach

Weak answer:

“I will report the defect.”

Strong answer:

Check logs

Verify request payload

Compare database records

Validate headers

Analyze backend logic

Reproduce the issue

Check dependent services

Interviewers heavily evaluate troubleshooting ability at this level.

6. No Real-Time Scenario Thinking

Many candidates memorize definitions but struggle with practical questions.

Common interview scenarios:

API returns 200 but wrong data — what do you do?

Payment deducted but order not created — what testing applies?

Retry creates duplicate records — how prevent it?

Interviewers prefer practical thinking over memorized theory.

7. Weak Understanding of Authentication

Candidates commonly confuse:

Authentication

Authorization

JWT tokens

Bearer tokens

401 vs 403

These are among the most frequently asked API interview topics.

You should clearly understand:

How tokens work

How tokens expire

How tokens are passed

Role-based access control

8. No Automation Awareness

Some candidates think API testing means only manual testing in Postman.

But modern projects increasingly expect:

Basic automation knowledge

Assertions

API automation awareness

CI/CD basics

Even simple knowledge of:

Rest Assured

Python requests

Newman

creates a stronger profile.

9. Weak Assertions

Some candidates validate only:

pm.response.to.have.status(200);

Interviewers expect stronger validations such as:

Schema validation

Field validation

Business rule validation

Header validation

Range validation

Assertions should validate meaningful behavior, not just technical success.

10. Explaining “What” but Not “Why”

Weak answer:

“I validated response fields.”

Better answer:

“I validated totals and discounts because incorrect calculations may cause financial defects.”

Interviewers value reasoning and risk awareness.

Q4. Freshers focus?
Freshers should focus on strong fundamentals and practical understanding, not advanced automation frameworks.

Most interviewers do NOT expect deep expertise from freshers.
They mainly check:

clarity of concepts,

logical thinking,

and willingness to learn.

1. Understand API Basics Clearly

This is the most important area.

You should confidently explain:

What is an API?

What is API testing?

REST vs SOAP

Request vs response

Endpoint

Payload

Headers

Status codes

These are asked in almost every interview.

2. Learn HTTP Methods

Know the purpose of:

Method	Purpose
GET	Retrieve data
POST	Create data
PUT	Full update
PATCH	Partial update
DELETE	Remove data

Interviewers frequently ask:

“Difference between PUT and PATCH?”

3. Practice in Postman

This is the best tool for beginners.

Practice:

Sending requests

Adding headers

Passing tokens

Validating responses

Testing positive and negative scenarios

You do NOT need advanced automation initially.

4. Learn Status Codes Properly

Must know:

Code	Meaning
200	Success
201	Created
400	Bad Request
401	Unauthorized
403	Forbidden
404	Not Found
500	Server Error

Interviewers ask these very often.

5. Understand Authentication

Very important topic.

Learn:

Bearer Token

API Key

OAuth basics

Authentication vs Authorization

Most APIs are secured.

6. Practice Response Validation

Do not say:

“I only checked status code.”

Instead explain validations like:

Response body

Schema

Business logic

Headers

Authentication

Response time

Interviewers like candidates who think beyond HTTP 200.

7. Learn Basic JSON

You should comfortably read JSON.

Example:

{
“id”: 101,
“name”: “Ravi”,
“status”: “ACTIVE”
}

Understand:

Key-value pairs

Arrays

Nested objects

8. Know Basic SOAP Concepts

Even if you focus mainly on REST, know:

What is SOAP?

What is XML?

What is WSDL?

SOAP vs REST

Many interviews still ask SOAP basics.

9. Practice Real-Time Scenarios

This is where candidates stand out.

Prepare answers for:

API returns 200 but wrong data

Expired token still works

Duplicate records created

API slow in production

Unauthorized access issue

Interviewers care a lot about logical thinking.

10. Learn Basic Automation Awareness

Freshers usually do NOT need advanced automation.

But basic awareness helps.

Example:

pm.response.to.have.status(200);

Knowing simple Postman assertions is enough for many fresher interviews.

11. Focus More on Practical Understanding Than Memorization

Weak answer:

“API testing validates APIs.”

Better answer:

“I validate status codes, response data, authentication, business logic, and negative scenarios.”

Practical explanations create stronger impact.

12. Learn Common Tools

At minimum, know basics of:

Postman

SoapUI (basic awareness)

Postman is the highest priority for freshers.

Q5. How to prepare fast?
If you have limited time, focus on the highest-impact topics first instead of trying to learn everything deeply.

For most QA/API interviews, strong fundamentals + practical thinking are enough.

1. Learn Core API Concepts First

These are asked in almost every interview.

Must know:

What is API?

What is API testing?

REST vs SOAP

Endpoint

Payload

Headers

Request vs Response

Status codes

Authentication

If these basics are weak, advanced topics will not help.

2. Master HTTP Methods

Very important.

Understand:

Method	Purpose
GET	Retrieve data
POST	Create resource
PUT	Full update
PATCH	Partial update
DELETE	Remove resource

Most interviewers ask:

“Difference between PUT and PATCH?”

3. Practice Using Postman

This gives the fastest practical improvement.

Practice:

Sending requests

Adding headers

Passing tokens

Validating responses

Running collections

Negative testing

Do NOT spend too much time on advanced automation initially.

4. Learn Status Codes Properly

Must know:

Code	Meaning
200	Success
201	Created
400	Bad Request
401	Unauthorized
403	Forbidden
404	Not Found
500	Server Error

These are extremely common interview questions.

5. Focus on Response Validation

Interviewers dislike answers like:

“I only checked 200 status.”

Instead explain validations such as:

Response body

Business logic

Headers

Authentication

Schema

Response time

This immediately makes answers stronger.

6. Practice Real-Time Scenario Questions

This is the fastest way to improve interview performance.

Prepare answers for:

API returns 200 but wrong data

Token expired but API still works

Duplicate records created

API works in Postman but fails in UI

Unauthorized access issue

Payment deducted but order not created

Interviewers heavily focus on these.

7. Learn Basic JSON

Very important.

Practice reading:

{
“id”: 101,
“name”: “Ravi”,
“status”: “ACTIVE”
}

Understand:

Objects

Arrays

Nested values

Most REST APIs use JSON.

8. Learn Authentication Basics

Know:

Bearer Token

API Key

OAuth basics

Authentication vs Authorization

Authentication questions are extremely common.

9. Learn SOAP Basics Only

For fast preparation, you do NOT need deep SOAP expertise.

Just know:

What is SOAP?

SOAP vs REST

XML basics

WSDL

SOAP Fault

Enough for many interviews.

10. Learn Basic Automation Awareness

Only basics are needed initially.

Example Postman script:

pm.response.to.have.status(200);

Understanding simple assertions is enough for many fresher and manual QA roles.

11. Practice Explaining Answers Clearly

Interviewers prefer:

simple,

structured,

practical explanations.

Weak answer:

“API testing validates APIs.”

Better answer:

“API testing validates requests, responses, authentication, business rules, status codes, and backend behavior.”

Clear communication matters a lot.

12. Use Real APIs for Practice

Best fast-learning method:

Open Postman

Test public APIs

Observe responses

Validate data

Break requests intentionally

Hands-on practice improves confidence very quickly.

Introduction – Why API Testing Is Important in Interviews

Leave a Comment Cancel Reply