Mock servers

A mock server answers requests with responses you prepared, instead of a real backend. Front-end developers can start before the API is finished, tests can run without a database, and you can try error cases that are hard to cause for real.

Mocks answer with a collection's saved examples. To add one, send a request and click Save as example, or create one by hand in the request's examples list. Save a few per endpoint: a success, a 404, a validation error.

A mock in the cloud

1. Open Mocks in the left sidebar and click +.
2. Pick the collection (and optionally an environment for {{variables}} in the examples).
3. Copy the mock's URL and use it as your API's base URL.

When a request comes in, the mock finds the example whose method and path match (/orders/42 matches an example saved for /orders/:id), the closest query and body, and answers with its status, headers and body.

Choose the response

Send these headers to pick a specific example:

• x-mock-response-code: 404 for the example with that status;
• x-mock-response-name: Out of stock for an example by name;
• x-mock-response-delay: 2000 to wait 2 seconds first, to see how your app handles a slow API.

Responses that use the request

Examples can copy values from the incoming request:

{ "id": "{{$pathSegments '1'}}", "status": "paid", "email": "{{$body 'customer.email'}}" }

{{$queryParams 'page' '1'}} and {{$headers 'X-Request-Id'}} work the same way, with an optional default value.

A mock on your computer

swc mock runs the same mock locally, with no account and nothing leaving your machine:

swc mock shop.json --port 4010

✓ mock of "Shop" on http://127.0.0.1:4010  (3 route(s) with examples, Ctrl+C to stop)
  GET /orders/{id} (2 examples)

It uses exactly the same matching and the same headers as the cloud mock, prints every request it answers, and allows browser calls from any port (CORS), so a front end on localhost:5173 can use it directly. A request no example matches gets a 404 listing the routes the mock knows.

What you learned

• Mocks answer from saved examples; headers pick the status, the example and a delay.
• Run them in the cloud for a shareable URL, or locally with swc mock.

Next: watch your API around the clock and see how reliable it really is.