text: self.onmessage = event => {
    // Checking for a particular value, so more tests can be added in future.
    if (event.data !== 'test-shownotification') return;
  
    // Random number, so we can identify the notification we create.
    const random = Math.random().toString();
    const start = Date.now();
  
    event.waitUntil(
      self.registration.showNotification('test', {
        tag: random,
        // ?pipe=trickle(d2) delays the icon request by two seconds
        icon: 'icon.png?pipe=trickle(d2)'
      }).then(() => {
        const resolveDuration = Date.now() - start;
  
        return self.registration.getNotifications().then(notifications => {
          event.source.postMessage({
            type: 'notification-data',
            resolveDuration,
            // Check if our notification is in notifications
            notificationReturned: notifications.some(n => n.tag == random)
          });
        });
      })
    );
  };