Mock request-promise for Jest by first recording real API requests and then reusing them in tests offline.

request-promise.js

'use strict'

/**
 * Makes it easy to record real API requests and save
 * them as mocks, which can then be reused.
 *
 * Usage inside Jest test file:
 * - first create a folder request-promise-mocks adjacent
 *   to this file (request-promise.js)
 * - turn the flag on in a test to use real API:
 *
 * const rp = require('request-promise')
 * rp.useMock = false
 *
 * - remove the flag code once you're done
 */

const _ = require('lodash')
const crypto = require('crypto')
const fs = require('fs')
const { promisify } = require('util')
const realRequire = require.requireActual('request-promise')

const readFile = promisify(fs.readFile)
const writeFile = promisify(fs.writeFile)

function request (options) {
  const optionsString = JSON.stringify(options, null, 2)
  const name = crypto.createHash('md5').update(optionsString).digest('hex')
  const mockFilePath = `${__dirname}/request-promise-mocks/${name}.json`

  if (!request.useMock) {
    return realRequire(options).then(response => {
      const responseJSON = JSON.stringify(response, null, 2)
      console.log(`---- REQUEST:
      ${optionsString}
      ---- RESPONSE:
      ${responseJSON}
      --------------
      `)
      return writeFile(mockFilePath, responseJSON)
      .then(() => response)
    })
  }

  return readFile(mockFilePath, 'utf8')
  .then(mockResponse => JSON.parse(mockResponse))
  .catch(err => {
    console.error('Mock for request could not be loaded', optionsString)
    throw err
  })
}

request.useMock = true

module.exports = request