Using with puppeteer
With the Global Setup/Teardown and Async Test Environment APIs, Jest can work smoothly with puppeteer.
Generating code coverage for test files using Puppeteer is currently not possible if your test uses
page.$eval
,page.$$eval
orpage.evaluate
as the passed function is executed outside of Jest's scope. Check out issue #7962 on GitHub for a workaround.
Use jest-puppeteer Preset
Jest Puppeteer provides all required configuration to run your tests using Puppeteer.
- First, install
jest-puppeteer
yarn add --dev jest-puppeteer
- Specify preset in your Jest configuration:
{
"preset": "jest-puppeteer"
}
- Write your test
describe('Google', () => {
beforeAll(async () => {
await page.goto('https://google.com');
});
it('should be titled "Google"', async () => {
await expect(page.title()).resolves.toMatch('Google');
});
});
There's no need to load any dependencies. Puppeteer's page
and browser
classes will automatically be exposed
See documentation.
Custom example without jest-puppeteer preset
You can also hook up puppeteer from scratch. The basic idea is to:
- launch & file the websocket endpoint of puppeteer with Global Setup
- connect to puppeteer from each Test Environment
- close puppeteer with Global Teardown
Here's an example of the GlobalSetup script
// setup.js
const fs = require('fs');
const os = require('os');
const path = require('path');
const mkdirp = require('mkdirp');
const puppeteer = require('puppeteer');
const DIR = path.join(os.tmpdir(), 'jest_puppeteer_global_setup');
module.exports = async function () {
const browser = await puppeteer.launch();
// store the browser instance so we can teardown it later
// this global is only available in the teardown but not in TestEnvironments
global.__BROWSER_GLOBAL__ = browser;
// use the file system to expose the wsEndpoint for TestEnvironments
mkdirp.sync(DIR);
fs.writeFileSync(path.join(DIR, 'wsEndpoint'), browser.wsEndpoint());
};
Then we need a custom Test Environment for puppeteer
// puppeteer_environment.js
const fs = require('fs');
const os = require('os');
const path = require('path');
const puppeteer = require('puppeteer');
const NodeEnvironment = require('jest-environment-node');
const DIR = path.join(os.tmpdir(), 'jest_puppeteer_global_setup');
class PuppeteerEnvironment extends NodeEnvironment {
constructor(config) {
super(config);
}
async setup() {
await super.setup();
// get the wsEndpoint
const wsEndpoint = fs.readFileSync(path.join(DIR, 'wsEndpoint'), 'utf8');
if (!wsEndpoint) {
throw new Error('wsEndpoint not found');
}
// connect to puppeteer
this.global.__BROWSER__ = await puppeteer.connect({
browserWSEndpoint: wsEndpoint,
});
}
async teardown() {
await super.teardown();
}
getVmContext() {
return super.getVmContext();
}
}
module.exports = PuppeteerEnvironment;
Finally, we can close the puppeteer instance and clean-up the file
// teardown.js
const os = require('os');
const path = require('path');
const rimraf = require('rimraf');
const DIR = path.join(os.tmpdir(), 'jest_puppeteer_global_setup');
module.exports = async function () {
// close the browser instance
await global.__BROWSER_GLOBAL__.close();
// clean-up the wsEndpoint file
rimraf.sync(DIR);
};
With all the things set up, we can now write our tests like this:
// test.js
const timeout = 5000;
describe(
'/ (Home Page)',
() => {
let page;
beforeAll(async () => {
page = await global.__BROWSER__.newPage();
await page.goto('https://google.com');
}, timeout);
it('should load without error', async () => {
const text = await page.evaluate(() => document.body.textContent);
expect(text).toContain('google');
});
},
timeout,
);
Finally, set jest.config.js
to read from these files. (The jest-puppeteer
preset does something like this under the hood.)
module.exports = {
globalSetup: './setup.js',
globalTeardown: './teardown.js',
testEnvironment: './puppeteer_environment.js',
};
Here's the code of full working example.