Idempotent
// Definition
An operation is idempotent if calling it multiple times produces the same result as calling it once. In REST, GET, PUT, DELETE, and HEAD are designed to be idempotent; POST is not. Idempotency matters for testing because you can safely retry a failed test step without fear of side effects. It also matters for test design: idempotent API calls make it straightforward to reset state between test runs.
// Related terms
REST
Representational State Transfer — an architectural style for HTTP APIs where resources are addressed by URLs and manipulated via standard HTTP verbs (GET, POST, PUT, DELETE). The dominant API style for over a decade.
Endpoint
A specific URL exposed by an API that accepts requests and returns responses. Defined by its path, HTTP method, and contract.
Status Code
A three-digit HTTP response code indicating outcome — 2xx success, 3xx redirect, 4xx client error, 5xx server error. The first signal an API test asserts on.