Run your mocha tests in headless chrome using puppeteer
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Since the release of Google Chrome headless mode, the Chrome DevTools team has developed puppeteer for running and managing an instance of Chromium. This module makes it possible to easily run tests written with mocha inside of a Chromium instance. Module bundling is automatically handled using lasso.


npm i -D mocha-puppeteer


Write your tests like you normally would with mocha.

const assert = require('assert')

describe('my test', () => {
  it('should pass', () => {
    assert(1 + 1 === 2)

To run your tests, you can pass in the test files to the exposed cli tool. A glob works too depending on the shell you are using.

npx mocha-puppeteer ./tests/dirA/*.js ./test/dirB/*.js

You can also just pass in a directory containing all of the tests you want to run.

npx mocha-puppeteer ./tests

You can also get test coverage information using nyc

npx nyc mocha-puppeteer ./test/*.js

All available options:

Usage: mocha-puppeteer [OPTIONS]


   Test a single file: "mocha-puppeteer /foo/bar-test.js"

   Test a series of files using a glob pattern: "mocha-puppeteer /foo/*/*-test.js"

   Test using Chromium args: "mocha-puppeteer /foo/bar-test.js --args account-consistency browser-startup-dialog"


             --help -h Show this help message [string]

          --version -v Show the version number of mocha-puppeteer [string]

     --testPagePath -P Path to a custom Marko test page [string]

        --pattern -p * Pattern to run tests. Either a single file or glob pattern. [string]

         --reporter -r The mocha test reporter to use. (Defaults to "spec") [string]

        --useColors -c Whether use colors for test output. (Defaults to true) [boolean]

               --ui -u The mocha ui to use. (Defaults to "bdd") [string]

--ignoreHTTPSErrors -i Whether to ignore HTTPS errors during navigation. Defaults to false. [boolean]

         --headless -H Whether to run Chromium in headless mode. Defaults to true. [boolean]

   --executablePath -e Path to a Chromium executable to run instead of bundled Chromium. If executablePath is a relative path, then it is resolved relative to current working directory. [string]

           --slowMo -s Slows down Puppeteer operations by the specified amount of milliseconds. Useful so that you can see what is going on. [number]

             --args -a Additional arguments to pass to the Chromium instance. List of Chromium flags can be found at [string]

     --handleSIGINT -S Close chrome process on Ctrl-C. Defaults to true. [boolean]

 --puppeteerTimeout -t Maximum time in milliseconds to wait for the Chrome instance to start. Defaults to 30000 (30 seconds). Pass 0 to disable timeout. [number]

           --dumpio -d Whether to pipe browser process stdout and stderr into process.stdout and process.stderr. Defaults to false. [boolean]

      --userDataDir -D Path to a User Data Directory. [string]

--puppeteerPageTimeout Maximum time in milliseconds to wait for the page to load [number]

NOTE: To use args Chromium flags, do not supply the prefixed double dash. Example of using args: mocha-puppeteer /foo/bar-test.js --args account-consistency browser-startup-dialog

Configuring the test file

You can configure mocha-puppeteer with a .mocha-puppeteer-config.js file.

Example config file:


module.exports = {
  mochaOptions: {
    reporter: 'nyan'

  lassoConfig: {
    require: {
      transforms: [
          transform: 'lasso-babel-transform'

  lassoDependencies: [

You can also get test coverage information using nyc

npx nyc mocha-puppeteer ./test/*.js

At the moment, you can specify mochaOptions, lassoConfig, and lassoDependencies. lassoDependencies will be included before test files. So any globals Babel transforms can be applied using the lasso-babel-transform module.

Note: Values provided in the mochaOptions field will be overridden by cli arguments. For example, mocha-puppeteer test/test.js --reporter dot will override the reporter option in the above config.

Executing page commands from tests

puppeteer page commands can be executed using window.puppeteerCommand from your tests. For example, if you want to take a screenshot of the page:

describe('screenshot test', function () {
  it('should take a screenshot', async () => {
    await window.puppeteerCommand({
      type: 'screenshot', // The page command to run
      args: [ {           // The arguments that should be passed to the page command
        path: './test.png'
      } ]

Advanced Usage

If you need to customize the page that is sent to the browser with your Mocha test code, you can do so, by specifiying a --testPagePath CLI option. mocha-puppeteer uses Marko.js for templating and Lasso to bundle browser dependencies. Provide a path to a Marko template similar to the following:


lasso-page [

<!DOCTYPE html>
    div id='mocha'


If you find a bug or have an idea about how to improve the module, please create an issue. If you have a fix for a bug, feel free to submit a pull request.

You can run tests with the npm test command.