support.js

import fs from 'fs-extra'
import path from 'path'
import cheerio from 'cheerio'
import Promise from 'bluebird'
import _ from 'lodash'
import { spawn as spawnNative } from 'child_process'
const remove = Promise.promisify(fs.remove)
const gatsbyCli = path.resolve(`..`, `..`, `lib`, `bin`, `cli.js`)
const babel = path.resolve(`..`, `..`, `node_modules`, `.bin`, `babel-node`)

export function spawn (command, args = [], options = {}) {
  return new Promise((resolve, reject) => {
    let stdout = ``
    let stderr = ``
    const child = spawnNative(command, args, options)
    child.stdout.on(`data`, data => { stdout += data })
    child.stderr.on(`data`, data => { stderr += data })
    child.on(`error`, error => reject({ error, stderr, stdout }))
    child.on(`exit`, code => {
      if (code === 0) {
        resolve({ code, stdout, stderr })
      } else {
        reject({ code, stdout, stderr })
      }
    })
  })
}

export function gatsby (args = [], options = {}) {
  const spawnArguments = _.concat([`--`, gatsbyCli], args)
  return spawn(babel, spawnArguments, options)
}

export function build (fixturePath) {
  const buildPath = path.resolve(fixturePath, `public`)
  return remove(buildPath)
    .then(() => gatsby([`build`], { cwd: fixturePath }))
}

export function dom (filePath) {
  const readFile = Promise.promisify(fs.readFile)
  return readFile(filePath)
    .then(html => cheerio.load(html))
}