Testing HTTP Status Codes

HTTP status codes are a crucial part of the contract of a REST API. They provide a standardized, immediate signal to the client about the outcome of its request. Relying on status codes is far more robust than, for example, checking for a key named `'error'` in a response body that always has a `200 OK` status. Therefore, testing that your API returns the correct status codes under various conditions is essential. Your automated tests should cover a range of scenarios: **Success Codes**: For a successful `GET` or `PUT` request, you should assert that the status code is `200 OK`. For a successful `POST` that creates a new resource, you should assert `201 Created`. For a successful `DELETE` or a request that requires processing but has no content to return, you should assert `204 No Content`. **Client Error Codes**: These indicate that the client did something wrong. You should test that sending a request with missing or invalid data (e.g., a malformed JSON body) returns `400 Bad Request`. Trying to access a resource that requires authentication without providing credentials should return `401 Unauthorized`. Trying to access a protected resource with valid credentials but insufficient permissions should return `403 Forbidden`. Requesting a resource that doesn't exist (e.g., `GET /users/9999`) should return `404 Not Found`. **Server Error Codes**: While harder to test deliberately, it's important that your API's global error handler correctly catches unexpected exceptions and returns a generic `500 Internal Server Error` instead of crashing or leaking stack traces. Thoroughly testing these codes ensures your API is predictable and easy for client developers to work with.