Categories
e2e Testing Playwright

Playwright Test Runner

I’d previously shared how to set up Playwright with Jest as a test runner which enabled us to do some cool things like:

  • Parallel test execution,
  • Automatic retries,
  • HTML reports (using Jest Stare), and
  • Screenshots when failing

It turns out that Playwright now supports all of the features without having to use Jest! It’s called the Playwright Test Runner.

I went ahead and created a fork of my existing code to show how to set this up with the Playwright Test Runner.

Specifying Tests

Fortunately the syntax to specify tests is almost identical to Jest, but you don’t need to worry about spawning browser contexts yourself 😎

This Jest test:

jest.retryTimes(1)

test('can use xpath selectors to find elements', async () => {
  global.page = await pages.spawnPage()
  await nav.visitHomePage(global.page)
  await home.clickScissors(global.page)
}, jestTimeoutMS)

becomes:

const { test } = require('@playwright/test')

test('can use xpath selectors to find elements', async ({ page }) => {
  await nav.visitHomePage(page)
  await home.clickScissors(page)
})

Running in Parallel

Like Jest, Playwright automatically runs your tests in parallel, sharing isolated browser pages within browsers, and spawning browsers across test files. The time taken was pretty much identical:

Jest

 PASS  scenarios/example4.spec.js
 PASS  scenarios/example3.spec.js
 PASS  scenarios/example5.spec.js
 PASS  scenarios/api.spec.js
 PASS  scenarios/example2.spec.js
 PASS  scenarios/example.spec.js

Test Suites: 6 passed, 6 total
Tests:       10 passed, 10 total
Snapshots:   2 passed, 2 total
Time:        5.514 s

Playwright Test

Running 10 tests using 6 workers

  ✓ scenarios/api.spec.js:5:1 › [chromium] can GET a REST API and check response using approval style (590ms)
  ✓ scenarios/example.spec.js:4:1 › [chromium] can wait for an element to appear (3s)
  ✓ scenarios/example2.spec.js:4:1 › [chromium] can handle alerts (4s)
  ✓ scenarios/api.spec.js:12:1 › [chromium] can GET a REST API and check response using assertion style (587ms)
  ✓ scenarios/example3.spec.js:5:1 › [chromium] can check for errors when there should be none (1s)
  ✓ scenarios/example4.spec.js:5:1 › [chromium] can check for errors when there are present (1s)
  ✓ scenarios/api.spec.js:25:1 › [chromium] can POST a REST API and check response using approval style (536ms)
  ✓ scenarios/example5.spec.js:6:1 › [chromium] can use xpath selectors to find elements (988ms)
  ✓ scenarios/api.spec.js:32:1 › [chromium] can POST a REST API and check response using assertion style (545ms)
  ✓ scenarios/example.spec.js:9:1 › [chromium] can use an element that appears after on page load (220ms)


  10 passed (5s)

Automatic Retries

Jest supports automatic retries in the test itself:

jest.retryTimes(1)

In Playwright Test you can configure it globally or per run:

// playwright.config.js
module.exports = {
  use: {
    retries: 2
  }
}
npx playwright test --retries=3

HTML Reports

I couldn’t see HTML report output for Playwright Test – but there’s heaps of others like JSON and Junit (for CI).

Screenshots

Screenshots are easily configured for Playwright Test: for each test never, always or on failure (my preference).

module.exports = {
  use: {
    screenshot: 'only-on-failure'
  }
}

But wait there’s more

The Playwright Test Runner also has these very cool features:

Visual comparisons (visdifs)

test('can wait for an element to appear', async ({ page }) => {
  await nav.visitHomePage(page)
  await page.waitForSelector('#elementappearschild', { visible: true, timeout: 5000 })
  expect(await page.screenshot()).toMatchSnapshot('element-appears.png')
})

At any point in your tests you can take a screenshot and store this to visually compare with future runs with fine grained tweaking of matches. The best part about this, in my opinion, is these visuals are stored alongside your tests (not in some third party system) so you know exactly what you’re expecting to see 😎

The one downside is the screenshots are platform specific so when I checked in those generated on my Mac then CI failed as it was running on Linux and didn’t have the baseline files to compare to. I just downloaded the captured files from CircleCI and stored them as a baseline.

And it also supports other comparisons – similar to Jest snapshots I have previously demonstrated. You just need to stringify them first:

test('can GET a REST API and check response using approval style', async () => {
  const request = supertest('https://my-json-server.typicode.com/webdriverjsdemo/webdriverjsdemo.github.io')
  const response = await request.get('/posts')
  expect(response.status).toBe(200)
  expect(JSON.stringify(response.body)).toMatchSnapshot('posts.txt')
})

Closing Thoughts

I was pretty blown away by the Playwright Test runner. It offers everything Jest provides with less code I had to write, plus it has in built visual comparison tools that can also be extended to do API approval snapshot testing. Playwright is well becoming my e2e test automation tool of choice.

Show me the Code

Of course: code is here: https://github.com/alisterscott/playwright-test-demo

Passing CI here: https://app.circleci.com/pipelines/github/alisterscott/playwright-test-demo/7/workflows/fe13f579-1f53-4a01-834e-6a4e7388e22c

Categories
Automated Testing e2e Testing

Generating data for e2e automated tests

I generally prefer creating e2e automated tests that generate their own data so that the test is repeatable, more deterministic and less dependent on external data and factors which can change.


When writing automated e2e tests that generate data I’ve found there are two common approaches:

  1. Generate static data: this data remains the same between test runs2.
  2. Generate random data: this data can change each test run

An example of static data for a test would be:

const ContactModel = function () {
  return {
    firstName: 'Sammy',
    lastName: 'Snake',
    phoneType: 'MOBILE',
    phoneNumber: '0422888444',
    emailType: 'PERSONAL',
    email: 'sammy.snake@hotmail.com',
    type: 'INDIVIDUAL'
  }
}

and the same example using randomised data:

function pick (list) {
  return list[Math.floor(Math.random() * list.length)]
}

const ContactModel = function () {
  const firstName = pick(['Aaron', 'Becca', 'Charlie', 'Donna', 'Eckbert', 'Fred', 'Graham', 'Holly', 'Ignatius', 'Josephine'])
  const lastName = pick(['Aardvark', 'Bear', 'Cat', 'Dog', 'Eagle', 'Fox', 'Gorilla', 'Horse', 'Iguana', 'J'])
  return {
    firstName: firstName,
    lastName: lastName,
    phoneType: 'MOBILE',
    phoneNumber: `+${Math.round(Math.random() * 9999999999999)}`,
    emailType: 'PERSONAL',
    email: `${firstName.toLowerCase()}.${lastName.toLowerCase()}@${pick(['hotmail.com', 'yahoo.com', 'gmail.com', 'aol.com'])}`,
    type: 'INDIVIDUAL'
  }
}

Generally speaking I will choose static data when writing automated e2e tests as it’s more repeatable and consistent, however I still commonly see random generated data being used in automated e2e automated tests.

I think the reason is that varying data is a good exploratory testing technique to find bugs, however automated e2e tests aren’t about exploring functionality but rather ensuring the functionality continues to work as expected (regression testing).

They don’t have to be completely separate concepts though, my checked-in automated e2e test can use static data so it’s consistent and repeatable, but I could modify the same automated test to use randomly generated input which I could specifically run looped for a large number of iterations to assist me with my exploratory testing and try to find bugs around input.

I’ve found that great testers uses automated tests as a technique to assist them with their exploratory testing.


What’s your preferred approach? Do you generate static or randomised data or use existing data for your automated e2e tests?

Categories
e2e Testing

Playwright + Jest = 💖

We were looking at a possible replacement for our dated Protractor + Cucumber e2e testing framework. As we move away from Angular to React microapps we have found that Protractor doesn’t work very well/efficiently and cucumber isn’t giving us any benefits.

It was a good opportunity to do some research/tinkering to answer the question lingering in my mind: in 2020 what e2e testing tool would I use by default for a dynamic react based web application?

After some experimentation it came down to Puppeteer + Jest or Playwright + Jest. I’ll compare those in this post.

Why Jest?

As explained previously we don’t need a BDD framework, but we do need something that allows us to specify our tests, create assertions and run these tests (in parallel). Jest, particularly when using the Jest Circus test runner, seems the most mature tool in this regard in 2020. Whilst Jest is often associated with React as it handles the snapshot test results also, it doesn’t need to be used with React and it’s possible and easy to use it as a standalone Node.js testing library.

Parallel Support

Jest by default runs tests across files in parallel and uses the available resources to scale appropriately using processes/threads. I’ve found this particularly good as I write independent e2e tests which can scale through parallelism, and using Puppeteer and Playwright you can spawn new incognito browser contexts to run these.

Auto-Retry Support

Whilst I believe in writing deterministic e2e automated tests, since e2e tests are full-stack there are often external dependencies and services beyond our control (like a third party domain provider) and I’d rather prioritize test reliability over test perfection. With this mind I think it’s important to be able to automatically retry a single failing test scenario before failing a build, and the Jest Circus test runner supports this:

jest.retryTimes(1)

test('can wait for an element to appear', async () => {
  global.page = await pages.spawnPage()
  await nav.visitHomePage(global.page)
  await global.page.waitForSelector('#elementappearschild', { visible: true, timeout: 5000 })
}, jestTimeoutMS)

HTML Reports and Screenshots

Nice looking HTML reports are easy to achieve by using jest-stare and screenshots are easy to generate using Jest Circus hooks.

Playwright or Puppeteer?

I’m a fan of Puppeteer however Playwright is a much nicer browser automation library. Whilst it adds support for Firefox and Webkit, even if you’re running your e2e tests in one browser (Chromium) I’d still recommend Playwright over Puppeteer any day of the week. Here’s why:

Automatic Waiting

I’ve found the automatic waiting in Playwright just works™️ Especially when dealing with dynamically rendered react web apps I’ve found my Puppeteer code looks is full of page.waitFor calls to make it run reliably:

await page.waitFor('#loadedchild', { visible: true, timeout: 5000 })

Whilst this is occasionally necessary in Playwright (in particular waiting for an iFrame to switch into), I’ve found it’s almost never required which reminds me of good old Watir days.

Nicer API

Whilst the APIs are similar, Playwright is just nicer to use. Take grabbing some text from a div, in Puppeteer:

await page.goto(`${config.get('baseURL')}`)
await page.waitFor('#loadedchild', { visible: true, timeout: 5000 })
const element = await page.$('#loadedchild')
const text = await (await element.getProperty('textContent')).jsonValue()
expect(text).toBe('Loaded!')

In Playwright:

await page.goto(`${config.get('baseURL')}`)
const text = await page.textContent('#loadedchild')
expect(text).toBe('Loaded!')

Summary

If I was writing an e2e web testing framework from scratch in 2020 I would use Playwright + Jest. Playwright offers automatic waiting and a nice API, whilst Jest offers a solid runner with parallel support, automatic retries and the ability to easily generate HTML reports and capture screenshots.

I’ve created one repository for Playwright + Jest #
And another for Puppeteer + Jest to compare #

As an aside we put changing node libraries on hold for our e2e test framework and will look at some test infrastructure improvements instead.

Categories
e2e Testing

Puppeteer Jest Demo

I’m trying to work out what would be the ideal combination for an e2e web testing framework in Node.

I wanted to try Jest with Puppeteer (I’d previously used Mocha) and I also wanted to try avoiding Babel for transpiling and using JavaScript directly so I came up with this example on GitHub.

I think I’ll try using TypeScript for my next tinker project.