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Headless Testing with Playwright and Jest

headlesstesting profile image HeadlessTesting ・2 min read

Playwright is a NodeJS package which can be used to automate Chrome, Firefox, Edge and Safari browsers in a headless manner.

It is developed by the same team that created Puppeteer at Google and is now actively developed at Microsoft.

The advantage of using Headless Testing is that it uses a real browser, but is much faster to run your tests than for example Selenium.

The combination of Jest, which is a NodeJS test runner framework maintained by Facebook and Playwright makes for a very robust Headless Testing toolkit.

Installing jest-playwright
There's a jest-playwright NPM library which makes it easy to get started with Jest and Playwright.

The package comes in combination with a jest-playwright-preset which you can then use as a preset for Jest in jest.config.js.

To install these packages, please enter this command in your terminal:
npm install -D jest jest-playwright-preset playwright

Once you've included the Playwright preset, you can either run the tests on a browser on your computer, or connect it to an online browser grid.

module.exports = {
  rootDir: '.',
  testTimeout: 20000,
  testMatch: [
    '/*.spec.js'
  ],
  preset: 'jest-playwright-preset'
}

Configuring jest-playwright
To connect your tests to a Headless Browser grid, please specify the connectBrowserApp setting in a file called jest-playwright.config.js.

module.exports = {
    connectBrowserApp: {
        wsEndpoint: 'wss://chrome.headlesstesting.com/?token=[YOUR-API-TOKEN]&browserVersion=dev'
    }
}

This will instruct Jest Playwright to start and use a headless Chrome browser on the HeadlessTesting.com grid.

Running your first test with jest-playwright
Now you are ready to run your first test with Jest and Playwright.
To get started, please create a new test file sample.spec.js:

describe('Google', () => {
  beforeAll(async () => {
    await page.goto('https://google.com')
  })

  it('should display google text on page', async () => {
    await expect(page).toMatch('google')
  })
})

You can now run this sample test:
$ jest
Depending on whether you want to run this test locally or on a cloud platform, the test will start a headless browser and navigate to Google, finally verifying if the word google appears on the page.

expect-playwright
There's also a NPM package available called expect-playwright. This is a Jest utility matcher for Playwright. It exposes various matchers, making it easier and cleaner to write certain assertions in your test scripts.

To get started, you can install the library:
npm install -D expect-playwright

Now you can use various matchers:

await expect(page).toHaveText("h1", "HeadlessTesting.com")

The various matchers include:

  • toHaveSelector
  • toHaveText
  • toEqualText
  • toEqualValue

Great Combo
Jest and Playwright is a great combination to do Headless testing. Both frameworks are under active development and keep getting better.

Posted on by:

headlesstesting profile

HeadlessTesting

@headlesstesting

Interested in Automated testing with Puppeteer and Playwright.

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