Top 30 API Testing Interview Questions and Answers

Published by SoftwareTestPilot

PDF • 13 pages • Interview Guide • Intermediate • Interview Preparation

Published 3 November 2026 • Updated 3 November 2026

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A 13-page interview guide covering api testing foundations, methods and repeat requests, read the whole response, inputs, contracts and negative tests.

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Overview

This study guide covers core API testing interview concepts, including HTTP methods, status codes, response assertions, and request inputs across headers, paths, queries, and bodies. It details architectural differences between REST and SOAP, clarifies method semantics such as PUT versus PATCH, and examines idempotency, contract validation, and business invariants. Designed for QA interview preparation, the notes assist testers in structuring answers around concepts, concrete scenarios, verifications, and operational risks. Practical examples illustrate testing for authentication, authorization, JWT tokens, pagination, end-to-end workflows, asynchronous operations, retries, and concurrent updates.

What you'll learn

Differentiate HTTP method semantics including PUT, PATCH, POST, and idempotent behavior.
Validate status codes, headers, payloads, and business invariants beyond simple schema checks.
Distinguish authentication from authorization and test JWT claims against server rules.
Design negative tests using missing inputs, boundaries, and prohibited state transitions.
Verify pagination, filtering, sorting, and multi-step end-to-end workflow state transitions.
Test asynchronous APIs by polling job status endpoints until terminal completion.
Evaluate safe request retry strategies and idempotency keys after network timeouts.

Topics covered

api testing
interview questions
authentication
rate limits
negative testing

API testing foundations
Methods and repeat requests
Read the whole response
Inputs, contracts and negative tests
Authentication and authorization
Collections and workflows
Async operations and safe retries
Concurrency and rate limits

Selected preview

API testing foundations

Extract from the PDF pages of this resource.

Skills covered

API Testing
Interview Preparation
Authentication Testing

Who this resource is for

QA Engineers
Software Testers

Format and what you get

A downloadable PDF you can read on phone or laptop.
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