API Testing
Test REST, GraphQL and secure APIs end-to-end.
API testing is where the highest ROI in QA lives. APIs are faster to test than UIs, they break earlier when contracts drift, and a good API suite catches bugs before a single pixel is painted. This hub covers REST, GraphQL, security testing and the exact tools — Postman, REST Assured, RestSharp, Bruno and k6 — hiring managers screen for.
You will find deep guides on writing your first request, designing contract tests, mocking dependencies, and wiring an API suite into GitHub Actions so every pull request is gated. Start with the Postman tutorial if you are new, jump to the API interview questions pillar if you are prepping, and use the practice endpoints in our PilotAPI lab to build a portfolio.
Start with these pillar guides
The highest-value pages on the site for api testing.
Topics in API Testing
Focused clusters under this hub. Tap any topic to filter the article list.
Latest in API Testing
Latest Test Query Format: The Complete Guide for QA Engineers (SQL, API & Search)
The definitive test query format guide for QA — copy-paste SQL, REST/GraphQL and Postman templates, a UAT test-case wrapper, and a Google search operator cheat sheet you can ship today.
Read article5 Critical API Testing Mistakes That Let Lethal Bugs Slip Into Production (2026)
Only asserting HTTP 200 OK? The 5 lethal API testing mistakes that cause outages — BOLA/IDOR, schema drift, rate-limit flakes, hardcoded secrets and siloed CRUD — with production-grade Playwright + Zod TypeScript.
Read articleGraphQL API Testing Guide: Complete 2026 Handbook
Complete 2026 GraphQL API testing guide. Schema validation, query testing, mutation testing, security testing, and tooling for Jest, Postman, and Karate.
Read articleMicroservices Testing: Complete Strategy Guide (2026)
How to test microservices in 2026 — contract testing with Pact, integration testing with Testcontainers, service virtualization, chaos & E2E patterns with real examples.
Read article12 Best API Testing Tools for Enterprise (2026)
The 12 best API testing tools for enterprise teams in 2026. Postman, REST Assured, Karate, Pact, ReadyAPI, and more compared with pricing, scoring, and ROI.
Read articleRestSharp API Testing in C#: Complete Guide
Learn RestSharp API testing in C# with step-by-step examples in 2026. Setup, GET/POST/PUT/DELETE, authentication, JSON serialization, and CI/CD integration.
Read articleRestSharp C# API Automation: Complete 2026 Guide
Complete RestSharp C# API automation guide for 2026. Setup, CRUD operations, authentication, schema validation, mocking, and CI/CD integration.
Read articleREST Assured Java Tutorial: Complete 2026 Guide
Complete REST Assured Java tutorial for 2026. Setup, GET/POST/PUT/DELETE, authentication, JSON path, schema validation, reusable specs, and CI/CD integration.
Read article10 Best Free API Mock Testing Tools (2026 Comparison)
The 10 best free API mock testing tools in 2026. WireMock, MockServer, Postman Mock Servers, Hoverfly, Prism compared with setup, features, and best use cases.
Read articleTop 40 API Testing Interview Questions & Answers (2026)
Ace your API testing interview with 40 real-world questions covering REST, Postman, status codes, authentication, contract testing and more. Free, with hands-on examples.
Read articlePostman Interview Questions & Answers (2026): 35+ Real Questions for QA Engineers
35+ Postman interview questions for 2026 — collections, environments, variables, scripts, Newman, CI integration, mock servers, monitors and contract testing. With code snippets.
Read articleAPI Testing 2026 — Ultimate Free Guide (REST, GraphQL, Postman)
Complete API testing tutorial for 2026 — REST, GraphQL, Postman, REST Assured, contract, security, performance & CI/CD with copy-paste code and interview prep. Free.
Read articlePostman API Testing 2026 — Free Beginner to Advanced Tutorial
Free 2026 Postman tutorial — from first request to collections, environments, scripting, data-driven, Newman CLI, mock servers, monitors & CI/CD. Beginner to advanced.
Read article10 Best Postman Alternatives for API Testing (2026)
Top 10 Postman alternatives for API testing in 2026 — Insomnia, REST Assured, Bruno, Hoppscotch, Thunder Client, Karate, SoapUI, HTTPie, curl and ReadyAPI compared with features, pricing, and best use cases.
Read articleMicroservices Testing in 2026: The Complete Pillar Guide (Strategy, Tools, Examples & FAQ)
The definitive 2026 microservices testing guide — the honeycomb test model, contract testing with Pact, Testcontainers integration, WireMock service virtualization, chaos & observability testing, tool comparison and a 30-day rollout plan for real distributed systems.
Read articleJSONPath Cheat Sheet for API Testers (2026)
The complete JSONPath cheat sheet for API testers — filters, wildcards, recursion, and copy-paste examples for Postman, Rest Assured, and Playwright.
Read articleJMESPath vs JSONPath — Which One Should QA Engineers Use?
JMESPath vs JSONPath compared with real API testing examples. Learn when each shines and see side-by-side queries you can run in a free tester.
Read articleHow to Validate JSON API Responses in Postman (Complete Guide)
Validate REST responses with pm.expect, JSON schema, JSONPath, and JMESPath. A step-by-step Postman guide with copy-paste snippets and a free JSON tester.
Read articleFrom Chrome DevTools cURL to an Automated Test in 60 Seconds
The exact 5-step workflow QA engineers use to turn any DevTools request into a passing automated test in Playwright, Postman, or Rest Assured.
Read articleHow to Migrate a Postman Collection to Rest Assured (Java)
Step-by-step guide to converting a Postman collection to Rest Assured Java tests: folders, pm.test assertions, environments, and Maven setup.
Read articleHow to Decode and Verify JWT Tokens (2026 QA Guide)
Decode, verify, and debug JWT tokens the safe way. Covers HS256, RS256, ES256, JWKS lookup, expiry checks, and how to test JWT auth in Postman, Playwright, and Rest Assured.
Read articleTesting JWT Authentication in Postman, Playwright & Rest Assured (2026)
End-to-end guide to testing JWT auth flows: obtain, decode, tamper, expire, and reuse tokens across Postman collections, Playwright fixtures, and Rest Assured suites.
Read articleAPI Testing Complete Guide 2026 — REST, GraphQL, Contract & Beyond
The 2026 complete guide to API testing — REST fundamentals, Postman & Newman, REST Assured, GraphQL, contract testing with Pact, security & performance, plus interview prep.
Read articleREST Assured Tutorial for Java QA (2026 Complete Guide)
Master REST Assured with 20 real examples: GET/POST/PUT/DELETE, JSON schema validation, auth, filters, and the framework layer that makes API tests survive a rewrite.
Read articleContract Testing with Pact — Consumer & Provider (2026)
Pact contract testing explained: consumer-driven contracts, provider verification, the broker, and CI wiring that catches microservice breakages before they reach staging.
Read articlePostman Newman CLI — CI/CD Guide with GitHub Actions (2026)
Run Postman collections in CI with Newman: exit codes, HTML reports, environment secrets, parallel execution, and a copy-paste GitHub Actions workflow that fails builds on API regressions.
Read articleGraphQL API Testing — Queries, Mutations, Subscriptions (2026)
GraphQL breaks traditional REST test patterns. Learn field-level assertions, N+1 detection, schema drift, subscription testing over WebSockets, and how to security-test introspection.
Read articleAPI Testing — frequently asked questions
1.What is API testing?
2.Which is the best tool for API testing in 2026?
3.What are the types of API testing?
4.How do I test REST APIs step by step?
5.Do API testers need to know coding?
6.What is the difference between API testing and unit testing?
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External reference: ISTQB Foundation Level