Mocking a GraphQL API

Right-click a folder ▸ Add ▸ GraphQL server.

Configuring

Field	Role
Schema	The type definitions, in SDL
Mock resolvers	A JSON object whose keys are of the form `Type.field`, for example `Query.pets`
Resolver script	JavaScript receiving `(parent, args, context)`

The script wins over the canned values when it is filled in: that is what lets you vary the response according to the arguments received.

A GraphQL server item: the listening address, the SDL schema served, and the map of predefined resolvers, key Type.field → value

Canned values

The quickest route: the schema describes the shape, the resolvers give the content.

type Animal { id: ID!, nom: String!, espece: String! }
type Query { animaux: [Animal!]! }

{
  "Query.animaux": [
    { "id": "1", "nom": "Mistigri", "espece": "chat" },
    { "id": "2", "nom": "Rex", "espece": "chien" }
  ]
}

Resolver script

For when the response has to depend on the input:

// (parent, args, context)
if (args.espece) {
  return animaux.filter((a) => a.espece === args.espece);
}
return animaux;

Subscriptions

The subscriptions declared in the schema are served too: a client can connect to them and receive the messages emitted.

In a scenario

The GraphQL server and GraphQL server close actions host the service for the duration of the scenario. See Hosted servers.

What it is for

Developing a front end before the back end exists, reproducing an error response that is hard to provoke in staging, or freezing a data set for a deterministic test — without depending on a remote service.