index.test.js

/* eslint-env jest */
/* global jasmine */
import {
  nextServer,
  runNextCommand,
  startApp,
  stopApp,
  waitFor,
} from 'next-test-utils'
import webdriver from 'next-webdriver'
import { join } from 'path'

jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 5

const appDir = join(__dirname, '../')
let appPort
let server
let app

describe('Prefetching Links in viewport', () => {
  beforeAll(async () => {
    await runNextCommand(['build', appDir])

    app = nextServer({
      dir: join(__dirname, '../'),
      dev: false,
      quiet: true,
    })

    server = await startApp(app)
    appPort = server.address().port
  })
  afterAll(() => stopApp(server))

  it('should prefetch with link in viewport onload', async () => {
    let browser
    try {
      browser = await webdriver(appPort, '/')
      const links = await browser.elementsByCss('link[rel=prefetch]')
      let found = false

      for (const link of links) {
        const href = await link.getAttribute('href')
        if (href.includes('first')) {
          found = true
          break
        }
      }
      expect(found).toBe(true)
    } finally {
      if (browser) await browser.close()
    }
  })

  it('should prefetch with link in viewport when href changes', async () => {
    let browser
    try {
      browser = await webdriver(appPort, '/')
      await browser.elementByCss('button').click()
      await waitFor(2 * 1000)

      const links = await browser.elementsByCss('link[rel=prefetch]')
      let foundFirst = false
      let foundAnother = false

      for (const link of links) {
        const href = await link.getAttribute('href')
        if (href.includes('another')) foundAnother = true
        if (href.includes('first')) foundFirst = true
      }
      expect(foundFirst).toBe(true)
      expect(foundAnother).toBe(true)
    } finally {
      if (browser) await browser.close()
    }
  })

  it('should prefetch with link in viewport on scroll', async () => {
    let browser
    try {
      browser = await webdriver(appPort, '/')
      await browser.elementByCss('#scroll-to-another').click()
      await waitFor(2 * 1000)

      const links = await browser.elementsByCss('link[rel=prefetch]')
      let found = false

      for (const link of links) {
        const href = await link.getAttribute('href')
        if (href.includes('another')) {
          found = true
          break
        }
      }
      expect(found).toBe(true)
    } finally {
      if (browser) await browser.close()
    }
  })

  it('should prefetch with link in viewport and inject script on hover', async () => {
    let browser
    try {
      browser = await webdriver(appPort, '/')
      await browser.elementByCss('#scroll-to-another').click()
      await waitFor(2 * 1000)

      const links = await browser.elementsByCss('link[rel=prefetch]')
      let foundLink = false

      for (const link of links) {
        const href = await link.getAttribute('href')
        if (href.includes('another')) {
          foundLink = true
          break
        }
      }
      expect(foundLink).toBe(true)

      await browser.elementByCss('#link-another').moveTo()
      await waitFor(2 * 1000)

      const scripts = await browser.elementsByCss(
        // Mouse hover is a high-priority fetch
        'script:not([async])'
      )
      let scriptFound = false
      for (const aScript of scripts) {
        const href = await aScript.getAttribute('src')
        if (href.includes('another')) {
          scriptFound = true
          break
        }
      }
      expect(scriptFound).toBe(true)
    } finally {
      if (browser) await browser.close()
    }
  })

  it('should inject a <script> tag when onMouseEnter (even with invalid ref)', async () => {
    let browser
    try {
      browser = await webdriver(appPort, '/invalid-ref')
      await browser.elementByCss('#btn-link').moveTo()
      await waitFor(2 * 1000)

      const scripts = await browser.elementsByCss(
        // Mouse hover is a high-priority fetch
        'script:not([async])'
      )
      let scriptFound = false
      for (const aScript of scripts) {
        const href = await aScript.getAttribute('src')
        if (href.includes('another')) {
          scriptFound = true
          break
        }
      }
      expect(scriptFound).toBe(true)
    } finally {
      if (browser) await browser.close()
    }
  })

  it('should not have unhandledRejection when failing to prefetch on link', async () => {
    const browser = await webdriver(appPort, '/')
    await browser.eval(`(function() {
      window.addEventListener('unhandledrejection', function (err) {
        window.hadUnhandledReject = true;
      })
      window.next.router.push('/invalid-prefetch');
    })()`)

    expect(await browser.eval('window.hadUnhandledReject')).toBeFalsy()

    await browser.elementByCss('#invalid-link').moveTo()
    expect(await browser.eval('window.hadUnhandledReject')).toBeFalsy()
  })

  it('should not prefetch when prefetch is explicitly set to false', async () => {
    const browser = await webdriver(appPort, '/opt-out')

    const links = await browser.elementsByCss('link[rel=prefetch]')
    let found = false

    for (const link of links) {
      const href = await link.getAttribute('href')
      if (href.includes('another')) {
        found = true
        break
      }
    }
    expect(found).toBe(false)
  })

  it('should not duplicate prefetches', async () => {
    const browser = await webdriver(appPort, '/multi-prefetch')

    const links = await browser.elementsByCss('link[rel=prefetch]')

    const hrefs = []
    for (const link of links) {
      const href = await link.getAttribute('href')
      hrefs.push(href)
    }
    hrefs.sort()

    // Ensure no duplicates
    expect(hrefs).toEqual([...new Set(hrefs)])

    // Verify encoding
    expect(hrefs.some(e => e.includes(`%5Bhello%5D.js`))).toBe(true)
  })

  it('should not add an another observer for a prefetched page', async () => {
    // info: both `/` and `/de-duped` ref the `/first` page, which we don't
    // want to be re-fetched/re-observed.
    const browser = await webdriver(appPort, '/')
    await browser.eval(`(function() {
      window.calledPrefetch = false
      window.next.router.prefetch = function() {
        window.calledPrefetch = true
      }
      window.next.router.push('/de-duped')
    })()`)
    await waitFor(2 * 1000)
    const calledPrefetch = await browser.eval(`window.calledPrefetch`)
    expect(calledPrefetch).toBe(false)
  })
})