API Contract Test Against OpenAPI

Set up a contract test that fails when the server response no longer matches the OpenAPI schema. One endpoint first, then the pattern. API Spec file: [PATH] Endpoint: [METHOD PATH] Auth in the test: [HOW] Framework under test: [FRAMEWORK] DELIVER 1) How we load the spec and pick the operation. A response validator (name a maintained library or a small AJV setup) that checks status and JSON against the schema. 2) The test: start the app or call the handler, send a known payload, validate the response. A second test for the error schema (422). 3) What to do with additionalProperties: the spec should say no if we want to catch extra fields, and you will set that deliberately. 4) CI: this runs with the unit tests and does not need the production network. 5) The process rule: change the spec in the same PR as the behavior. The test is how that rule is enforced. Do not snapshot the whole JSON as the contract. The spec is the contract. Do not weaken the schema to make the test green.