GraphQL Testing Library provides utilities that make it easy to generate Mock Service Worker handlers for any GraphQL API.

MSW is the Testing Library-recommended way to declaratively mock API communication in your tests without stubbing window.fetch.

This library currently supports incremental delivery features @defer and @stream out of the box, with plans to support subscriptions over multipart HTTP as well as other transports such as WebSockets, currently in beta in MSW.

This project is not affiliated with the "Testing Library" ecosystem that inspired it. We're just fans :)

Installation

This library has peerDependencies listings for msw at ^2.0.0 and graphql at ^15.0.0 || ^16.0.0. Install them along with this library using your preferred package manager:

npm install --save-dev @apollo/graphql-testing-library msw graphql
pnpm add --save-dev @apollo/graphql-testing-library msw graphql
yarn add --dev @apollo/graphql-testing-library msw graphql
bun add --dev @apollo/graphql-testing-library msw graphql

Usage

createHandler

import { createHandler } from "@apollo/graphql-testing-library";

// We suggest using @graphql-tools/mock and @graphql-tools/schema
// to create a schema with mock resolvers.
// See https://the-guild.dev/graphql/tools/docs/mocking for more info.
import { addMocksToSchema } from "@graphql-tools/mock";
import { makeExecutableSchema } from "@graphql-tools/schema";
import typeDefs from "./schema.graphql";

// Create an executable schema
const schema = makeExecutableSchema({ typeDefs });

// Add mock resolvers
const schemaWithMocks = addMocksToSchema({
  schema,
  resolvers: {
    Query: {
      products: () =>
        Array.from({ length: 5 }, (_element, id) => ({
          id: `product-${id}`,
        })),
    },
  },
});

// `createHandler` returns an object with a `handler` and `replaceSchema`
// function: `handler` is a MSW handler that will intercept all GraphQL
// operations, and `replaceSchema` allows you to replace the mock schema
// the `handler` use to resolve requests against.
const { handler, replaceSchema } = createHandler(schemaWithMocks, {
  // It accepts a config object as the second argument where you can specify a
  // delay duration, which uses MSW's delay API:
  // https://mswjs.io/docs/api/delay
  // Default: "real" (100-400ms in browsers, 20ms in Node-like processes)
  delay: number | "infinite" | "real",
});