apollo-server-testing with headers

_test.js

const assert = require('assert').strict
const { ApolloServer, gql } = require('apollo-server-cloud-functions')

const server = new ApolloServer({
  typeDefs: gql`
    type Query {
      field: String
    }
  `,
})

const { createTestClient } = require('./apollo-testing')
const { query } = createTestClient(server)

query({
  query: gql`
    {
      __typename
    }
  `,
}).then(response => {
  assert.deepStrictEqual(
    response.body,
    { data: { __typename: 'Query' } },
    'body mismatch'
  )
  assert.deepStrictEqual(
    new Set([['content-length', '32'], ['content-type', 'application/json']]),
    new Set(response.http.headers),
    'Headers Mismatch'
  )
})

apollo-testing.js

const { print } = require('graphql/language/printer')
const { Headers } = require('node-fetch')
exports.createTestClient = server => {
  const handler = server.createHandler()
  const queryHandler = ({
    query,
    headers = {},
    variables = {},
    queryString,
    operationName,
  }) => {
    return new Promise(resolve => {
      handler(
        {
          headers: {
            'content-type': 'application/json',
            ...headers,
          },
          body: {
            operationName,
            query: queryString || print(query),
            variables,
          },
          method: 'POST',
          mode: 'cors',
        },
        {
          _headers: {},
          _status: 0,
          set(headers) {
            this._headers = { ...this._headers, ...headers }
            return this
          },
          status(status) {
            this._status = status
            return this
          },
          send(body) {
            resolve({
              http: {
                status: this._status,
                headers: new Headers({ ...this._headers }),
              },
              body: JSON.parse(body),
            })
          },
        }
      )
    })
  }
  return {
    query: queryHandler,
    mutate: queryHandler,
  }
}