A practical guide to API testing with JavaScript: Jest and Supertest for Node.js services, Playwright's request API for external APIs, JSON Schema validation with Ajv, and a CI workflow, all with runnable code.
How to test API versioning and backward compatibility: URI, header and media-type strategies, breaking vs non-breaking changes, OpenAPI diff tools like oasdiff, consumer contracts, deprecation headers and CI gates.
What JSON Schema validation is and how it works: the 2020-12 draft and its core rules, then runnable examples validating API responses in Python (jsonschema), JavaScript (Ajv), Java (networknt, REST Assured) and Postman, how it aligns with OpenAPI 3.1, and the errors you will hit.
A practical guide to OpenAPI and Swagger API testing: how spec-driven testing works, the six kinds of tests a spec makes possible, a worked pytest and Schemathesis example against the public Petstore API, CI wiring, tools, common mistakes and a checklist.
Twenty-one AI testing tools sorted into the five jobs they actually do — spec-driven API generation, traffic recording, UI maintenance, authoring assistants and LLM evals — with what each is good at, what it needs from you and what to verify in a trial.
The 10 best API mocking and service virtualization tools in 2026, compared across spec-driven, standalone stub server, and enterprise virtualization categories.
What an API testing framework actually is, the three real categories to choose between, and a practical decision framework based on team language, CI/CD needs, and who should be able to read the tests.
The 11 best API load testing tools in 2026, compared on scripting language, protocol support, CI/CD fit, and pricing model — free/open source and commercial.
A practical LLM testing method — deterministic shell versus probabilistic core, invariant and tolerance assertions, golden-set evals with thresholds, safety and bias tests, CI gates, governance and the open-source tools that fit each layer.
