GraphQL mock server

A GraphQL mock answers any valid query against a schema with fake but correctly typed data, so you can build a front end, write tests or demo a flow before the real API exists or while it is down.

From the app

1. In the GraphQL editor, enter the endpoint and click Introspect.
2. Click Mock. The mock starts on http://127.0.0.1:<port>/graphql and the URL is copied to the clipboard.
3. Point your app (or another GraphQL tab) at that URL. The button shows Mock on; click it again to stop.

Clicking Mock after introspecting a changed schema updates the running mock.

From the CLI

testpion mock-graphql --schema schema.graphql -p 4000
testpion mock-graphql --schema introspection.json --overrides fixtures.json
testpion mock-graphql --endpoint https://api.example.com/graphql --list-length 5

Option	Description
--schema <file>	Schema as SDL (.graphql) or an introspection result (.json).
--endpoint <url>	Or introspect a running GraphQL server.
-p, --port	Port (default: any free port).
--overrides <file>	Fixed values per type, see below.
--list-length <n>	Items in every list (default 2).
--delay <ms>	Delay every response, to test loading states.

What the data looks like

• Typed: every field returns a value of its type: IDs, numbers, booleans, a value of the enum, objects and lists. Interfaces and unions return one of their types, with __typename.
• Plausible: values follow the field name. email gets an email address, name a person's name, url / avatar a URL, createdAt / date an ISO date, price / amount a price, phone a phone number and status a status.
• Deterministic: the same query always returns the same data, so tests and screenshots are stable.
• Real errors: an invalid query gets the same validation errors a real server would send, with HTTP 400.
• Introspection works, so GraphQL clients and IDEs can explore the mock.

Fixed values (overrides)

Give fixed values per type in a JSON file. Other fields stay generated:

{
  "Patient": { "name": "Rex", "species": "DOG" },
  "Query": { "patients": [{ "name": "Rex" }, { "name": "Tom" }] }
}

The mock only listens on localhost.