Service Worker Mock

A mock service worker environment generator.

Why?

Testing service workers is difficult. Each file produces side-effects by calls to self.addEventListener, and the service worker environment is unlike a normal web or node context. This package makes it easy to turn any environment into a feaux service worker environment. Additionally, it adds some helpful methods for testing integrations.

The service worker mock creates an environment with the following properties, based on the current Mozilla Service Worker Docs.

const env = {
  // Environment polyfills
  skipWaiting: Function,
  caches: CacheStorage,
  clients: Clients,
  registration: ServiceWorkerRegistration,
  addEventListener: Function,

  // Test helpers
  listeners: Object,
  trigger: Function,
  snapshot: Function,
};

Test Helper	description
listeners	[Object] A key/value map of active listeners (install/activate/fetch/etc).
trigger	[Function] Used to trigger active listeners (await self.trigger('install')).
snapshot	[Function] Used to generate a snapshot of the service worker internals (see below).

Snapshot Property	description
caches	[Object] A key/value map of current cache contents.
clients	[Array] A list of active clients.
notifications	[Array] A list of active notifications

Use

The following is an example snippet derived from tests/basic.js. The test is based on the service worker example provided by Google.

const makeServiceWorkerEnv = require('service-worker-mock');

describe('Service worker', () => {
  it('should delete old caches on activate', async () => {
      Object.assign(global, makeServiceWorkerEnv());
      require('./path/to/sw.js');

      // Create old cache
      await self.caches.open('OLD_CACHE');
      expect(self.snapshot().caches.OLD_CACHE).toBeDefined();

      // Activate and verify old cache is removed
      await self.trigger('activate');
      expect(self.snapshot().caches.OLD_CACHE).toBeUndefined();
  });
});

License

MIT