REST APIs: Concepts and How to Test Them

REST (Representational State Transfer) is a common style for web APIs. As a QA, you need to understand resources, URLs, HTTP methods, and how to test REST endpoints. This post gives you the concepts and a testing angle.

REST in brief

• Resources: Things the API exposes (e.g. users, orders, products). Each resource has a URL (e.g. /users, /orders/123).
• HTTP methods: GET (read), POST (create), PUT/PATCH (update), DELETE (remove). Same URL can behave differently for different methods.
• Stateless: Each request carries what the server needs; no server-side session required (auth often via headers).

URLs and methods

• GET /users — list users.
• GET /users/1 — get user with id 1.
• POST /users — create user (body with data).
• PUT /users/1 or PATCH /users/1 — update user 1.
• DELETE /users/1 — delete user 1.

You test each method: valid and invalid inputs, permissions, and response format.

How to test REST APIs

• Positive: Valid request → expected status (e.g. 200, 201) and correct body/headers.
• Negative: Invalid input, missing auth, wrong method → expected error status (e.g. 400, 401, 404) and error body.
• Edge: Boundary values, empty list, missing optional fields.
• Idempotency and safety: GET and DELETE semantics; POST vs PUT when applicable.

Summary

• REST = resources (URLs) + HTTP methods (GET, POST, PUT/PATCH, DELETE); stateless.
• Test each endpoint for positive, negative, and edge cases; check status codes and response body.
• Use the next posts (HTTP details, Postman, test design) to build concrete test cases and automation.