Run Mocha Tests in Parallel

Run automated tests on multiple browsers in parallel with Mocha JS using BrowserStack Automate.

Introduction

On BrowserStack, you can run multiple Mocha tests at the same time across various browser, device, and OS combinations. This is called Parallel Testing. Parallel Testing gives you the same benefits as running a multi-threaded application.

With Parallel Testing, you can run the same test on different browser/device combinations, namely cross-browser testing, or run different tests on the same or different browser/device combinations. Parallel Testing helps you reduce the run time of your test suite, resulting in faster build times and faster releases.

In this guide, you will learn about:

1. Prerequisites
2. Running your first parallel test

Prerequisites

If you have already run your first test, you can skip the prerequisites.

• BrowserStack Username and Access key, which you can find in your account settings. If you have not created an account yet, you can sign up for a Free Trial or purchase a plan.
• Node.js installed on your machine.
• Git installed on your machine.
• NPM installed on your machine.
• Mocha JS installed on your machine using the npm command:

    npm install mocha
  

Run your first parallel test

1. Clone the mocha-browserstack sample repo on GitHub using the following command:
   
   

   git clone https://github.com/browserstack/mocha-browserstack.git
   cd mocha-browserstack
   

2. Open the cloned project in the IDE of your choice and install the required dependencies by running the following command in your command line:
   
   

    npm install
   

3. Set your BrowserStack credentials and browser/devices where you want to run your test in the mocha-browserstack/conf/parallel.conf.js file as follows:
   
   

   parallel.conf.js

    var config = {
      'commanCapabilities': {
        'browserstack.user': 'YOUR_USERNAME',
        'browserstack.key': 'YOUR_ACCESS_KEY',
        'build': 'mocha-browserstack',
        'name': 'parallel_test',
        'browserstack.debug': 'true',
      },
      'multiCapabilities': [{
          'os': 'Windows',
          'os_version': '10',
          'browserName': 'Chrome',
          'browser_version': 'latest',
          'name': 'Parallel test 1'
        },
        {
          'os': 'OS X',
          'os_version': 'Monterey',
          'browserName': 'Chrome',
          'browser_version': 'latest',
          'name': 'Parallel test 2'
        },
        {
          'os' : 'OS X',
          'os_version' : 'Big Sur',
          'browserName' : 'Safari',
          'name': 'Parallel test 3'
        },
        {
          'browserName': 'Android',
          'device': 'Samsung Galaxy S20',
          'realMobile': 'true',
          'name': 'Parallel test 4'
        },
        {
          'browserName': 'iPhone',
          'device': 'iPhone 12 Pro Max',
          'realMobile': 'true',
          'name': 'Parallel test 5'
      }]
    };
   
    exports.capabilities = [];
    // Code to support common capabilities
    config.multiCapabilities.forEach(function(caps) {
      var temp_caps = JSON.parse(JSON.stringify(config.commanCapabilities));
      for(var i in caps) temp_caps[i] = caps[i];
      exports.capabilities.push(temp_caps);
    });
   

4. Run your tests in parallel on BrowserStack using the following command:
   
   

    npm run parallel
   

5. Optionally, you can also choose to run your tests on other environments by specifying them in the multiCapabilities key of the mocha-browserstack/conf/parallel.conf.js configuration file as follows:

   'multiCapabilities': [{
        'browserName': 'Chrome',
        'browser_version': 'latest',
        'os': 'Windows',
        'os_version': '10'
      },{
        'device': 'iPhone 12 Pro',
        'browserName': 'iPhone',
        'os_version': '14'
      },{
        'browserName': 'safari'
        'browser_version': 'latest',
        'os': 'OS X',
        'os_version': 'Big Sur'
      },{
        'device': 'Samsung Galaxy S20 Ultra',
        'browserName': 'Android',
        'os_version': '10.0'
      }]
   

6. View your tests on BrowserStack on the BrowserStack Automate Dashboard.

Next steps

After you have successfully run your first parallel test using BrowserStack, you can explore the following sections:

• Plan the number of parallels you need
• What are queued tests in Parallel Testing on BrowserStack