karma-sw-mocha

A Karma plug-in, framework for Mocha testing when running inside a ServiceWorker.

What is Karma SW Mocha for?

Karma SW Mocha should be employed for performing tests in a ServiceWorkerGlobalScope and not in a window environment. It is not to test interceptions, nor performing integration tests between your client code and your service worker. It will simply run your code inside a special service worker and will warry about comunicating the results of the testing to the Karma reporter.

Installation

Install karma-sw-mocha from npm:

$ npm install --save karma-sw-mocha

And add it as the first item of your framework list in the Karma configuration file...

{
  frameworks: ['sw-mocha', /* other frameworks... */],
}

Notice the name of the framework is sw-mocha and not karma-sw-mocha.

Adding tests

For the service worker to know which test files should load, you need to add them to a special file sw-tests.js in the root of your project:

// sw-tests.js
var SW_TESTS = [
  '/base/path/to/your/tests/myTest.sw-spec.js'
];

Karma will serve all your files under the /base/ path. So if your tests are in test/test1.sw-spec.js and test/test2.sw-spec.js they should be added as:

// sw-tests.js
var SW_TESTS = [
  '/base/test/test1.sw-spec.js',
  '/base/test/test2.sw-spec.js'
];

Loading other libraries

A testing framework is usually insufficient to provide an efficient testing environment. You usually will need an assertion library like Chai and a spy / mock library as Sinon. You can install Karma versions of these libraries with:

$ npm install --save karma-sinon karma-chai

To include them in your service worker setup, edit sw-tests.js and import the proper scripts there:

// sw-tests.js
var SW_TESTS = [ /* your test files... */ ];
importScripts('/base/node_modules/chai/chai.js');
importScripts('/base/node_modules/sinon/pkg/sinon.js');

Don't forget to add these frameworks to your Karma configuration, after sw-mocha:

{
  frameworks: ['sw-mocha', 'sinon', 'chai']
}

Configuring mocha and running custom setup code

The file sw-tests.js will be load before executing any test so you can add there the code for loading custom scripts and your own custom synchronous setup code. For instance, you could instruct mocha to enable BDD API and make Chai's expect() globally available:

// sw-tests.js
var SW_TESTS = [ /* your test files... */ ];
 
importScripts('/base/node_modules/chai/chai.js');
// your other imports...
 
mocha.setup({ ui: 'bdd' });
self.expect = chai.expect;

Configuration example

In samples/mocha-sinon-chai-bdd you will find sample files for the Karma configuration file and sw-tests.js to set and Mocha BDD + Chai + Sinon environment up.

Enabling tests of Firefox

Currently only Firefox Nightly has support for Service Workers and only after turning on certain flags. You will need a custom launcher to enable SW on Nightly. Do it by replacing the Firefox launcher in your config file with some similar to this:

{
  browsers: ['NightlySW'],
 
  customLaunchers: {
    'NightlySW': {
      base: 'FirefoxNightly',
      prefs: {
        'devtools.serviceWorkers.testing.enabled': true,
        'dom.serviceWorkers.enabled': true
      }
    }
  }
}