Shortly after I finished writing my previous post, the same team behind Puppeteer released Playwright, a similar Node library with two notable differences – it offers cross-browser functionality out of the box, and is from Microsoft, not Google.

Playwright is essentially Puppeteer with cross-browser support – Chromium (Chrome, Edge), Webkit (Safari), and Firefox browsers can now be automated with a single API.

This post looks at setting up Playwright with a create-react-app generated app. It uses a Jest test runner and follows the page object model.

The sample project can be found on GitHub.

Contents

Running Specs

Let’s take a look at a sample project that’s set-up with Playwright. If you want to add this set-up to your current project, you can skip this section and go straight to Adding to an Existing Project.

Open a new terminal and run –

$ git clone https://github.com/kyleaday/react-app-playwright
$ cd react-app-playwright
$ npm install

In order to improve test readability and maintainability, I created a playwright.config.js file to set browser, launch and context options:

// e2e/playwright.config.js

import { chromium, firefox, webkit, devices } from 'playwright';

const iPhone = devices['iPhone 6'];

module.exports = {
    browserType: webkit,
    launchConfig: {
        headless: false,
        slowMo: 10
    },
    contextConfig: {
        viewport: iPhone.viewport,
        userAgent: iPhone.userAgent
    }
};

For example, this configuration sets Webkit as the browser type, turns off headless mode and sets a slowMo time. It also sets the context to emulate an iPhone 6, so when the tests are run, the screen-size adjusts accordingly. Other device properties can be set here, such as geolocation, permissions, etc.

As Playwright doesn’t automatically use my custom configuration file, I must pass these variables into the launch() and newContext() functions, which will be discussed further in Writing Specs and Page Objects.

The jest.config.js file is automatically used when running Jest, and this is where I’ve set the global baseURL: “http://localhost:3000”.

Now we’re ready to run some tests. Let’s start the app –

$ npm start

And open a new terminal to run the tests –

$ npm run e2e

The script e2e can be found in the package.json. It runs cd e2e && jest, which changes our directory to e2e, so Jest will use the correct configuration.

As we’re not running headless, the browser will load onscreen, navigate to the page and perform the tests.

Writing Specs and Page Objects

This project follows the page object model – the UI structure has been separated from the specs (or tests) for easier readability and maintainability. Spec files can be found in e2e/specs, and the accompanying page objects are in e2e/pageObjects.

Let’s look at the spec and page object for index.js

// e2e/specs/index.js

import { load, close, getTitle } from '../pageObjects';

describe("React App", () => {
    beforeEach(async () => {
        await load();
    });

    afterEach(async () => {
        await close();
    });

    it("should be titled 'React App'", async () => {
        expect(await getTitle()).toBe('React App');
    });
});

This spec imports the load method and the functions close and getTitle from the index.js page object file.

Jest API globals are used - describe groups the tests, the browser loads beforeEach test, and then closes afterEach test. The it method runs the tests and expect gives us access to validation matchers, in this example toBe.

The page object model makes the spec easy to read – it loads the page, gets the title, checks that the actual title matches the expected title, and finally closes the browser.

Let’s look at the page object –

// e2e/pageObjects/index.js

import { browserType, launchConfig, contextConfig } from '../playwright.config'

const rootSelector = '#root';
let browser, context, page;

export const root = async () => await page.$(rootSelector);

export const load = async () => {
    browser = await browserType.launch(launchConfig);
    context = await browser.newContext(contextConfig);
    page = await context.newPage(baseURL);
};

export const close = async () => await browser.close();

export const getTitle = async () => await page.title();

As mentioned earlier, Playwright doesn’t automatically use the playwright.config.js file, so our configuration variables must be imported before they can be used when launching our browser.

Let’s look closer at the load method -

export const load = async () => {
    browser = await browserType.launch(launchConfig);
    context = await browser.newContext(contextConfig);
    page = await context.newPage(baseURL);
};

The load method launches our browserType with the launchConfig, sets the context with the contextConfig and navigates to the baseURL page. The variables browser, context and page are then used elsewhere in the page object, such as browser.close(), page.$(selector) and page.title().

Like Puppeteer, the Playwright API has similar classes with methods that allow us to interact with a page. Playwright can automate most browser interactions, such as filling out forms, entering keystrokes, moving the mouse, and more. A list can be found here

Adding to an existing project:

To use this set-up on existing projects –

  • Copy the e2e folder into the root of the project -
$ cp -r react-app-playwright/e2e <react-app>
  • Install the additional dev dependencies -
$ npm install --save-dev playwright
  • Add the following script in the project’s package.json -
{
  // ...
  "scripts": {
    // ...
    "e2e": "cd e2e && jest",
  }
}

Playwright or Puppeteer?

That is the question. Even though Playwright does not have a jest-puppeteer package equivalent (yet!), it’s just as easy as to set-up. Puppeteer users will also be familiar with the Playwright API.

However, I have experienced slight teething problems with Playwright. For example, I’ve noticed that slowMo can be temperamental, and if set too high the tests often fail. The consistency of slowMo also seems to vary from browser to browser.

Puppeteer is the more established project at the moment, but if you need cross-browser functionality, then perhaps it’s time to make the switch to Playwright.

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