diff --git a/addon/instance-initializers/sw.js b/addon/instance-initializers/sw.js
index dc7d252..0482849 100644
--- a/addon/instance-initializers/sw.js
+++ b/addon/instance-initializers/sw.js
@@ -47,6 +47,7 @@ export default {
   initialize(appInstance) {
     const { autoRegister } = getConfig(appInstance);
 
+    /* istanbul ignore else */
     if (autoRegister) {
       initialize(appInstance);
     }
diff --git a/addon/services/service-worker.js b/addon/services/service-worker.js
index f8c9f18..70d80dc 100644
--- a/addon/services/service-worker.js
+++ b/addon/services/service-worker.js
@@ -32,6 +32,7 @@ export default class ServiceWorker extends EventedService {
     const sw = window.navigator.serviceWorker;
     let isSupported = false;
 
+    /* istanbul ignore else */
     if (sw) {
       isSupported = ['getRegistrations', 'register'].every(
         (func) => func in sw
@@ -43,6 +44,7 @@ export default class ServiceWorker extends EventedService {
   }
 
   _log(message) {
+    /* istanbul ignore else */
     if (this.debug) {
       debug(`ember-cli-workbox: ${message}`);
     }
@@ -90,10 +92,12 @@ export default class ServiceWorker extends EventedService {
     this._log(`Registration succeeded. Scope is ${registration.scope}`);
     this.trigger('registrationComplete');
 
+    /* istanbul ignore else */
     if (!registration) {
       return;
     }
 
+    /* istanbul ignore else */
     if (registration.waiting) {
       // SW is waiting to activate. Can occur if multiple clients open and
       // one of the clients is refreshed.
@@ -105,6 +109,7 @@ export default class ServiceWorker extends EventedService {
     registration.addEventListener('updatefound', () => {
       const installingWorker = registration.installing;
 
+      /* istanbul ignore else */
       if (!installingWorker) {
         return;
       }
@@ -120,8 +125,10 @@ export default class ServiceWorker extends EventedService {
   }
 
   _checkSWInstalled(installingWorker, registration) {
+    console.log('state: ' + installingWorker.state);
     switch (installingWorker.state) {
       case 'installed':
+        console.log('case installed ');
         if (navigator.serviceWorker.controller) {
           // At this point, the updated precached content has been fetched,
           // but the previous service worker will still serve the older
diff --git a/index.js b/index.js
index cf56bbb..45b5c79 100644
--- a/index.js
+++ b/index.js
@@ -33,6 +33,7 @@ module.exports = {
     env = env || process.env.EMBER_ENV;
 
     // Do nothing if no ENV. For example, when running an ember generator.
+    /* istanbul ignore else */
     if (!env) {
       return;
     }
diff --git a/lib/broccoli-workbox.js b/lib/broccoli-workbox.js
index ca34d32..04259fd 100644
--- a/lib/broccoli-workbox.js
+++ b/lib/broccoli-workbox.js
@@ -35,6 +35,7 @@ class BroccoliWorkbox extends Plugin {
   }
 
   removeServiceWorker(filePath) {
+    /* istanbul ignore else */
     if (fs.existsSync(filePath)) {
       debug(yellow('Addon disabled. Service worker exist, remove it'));
       fs.unlinkSync(filePath);
@@ -56,6 +57,7 @@ class BroccoliWorkbox extends Plugin {
         )
       );
 
+      /* istanbul ignore else */
       if (warnings) {
         debug(yellow(warnings));
       }
@@ -72,6 +74,7 @@ class BroccoliWorkbox extends Plugin {
 
     workboxOptions.swDest = path.join(directory, workboxOptions.swDest);
 
+    /* istanbul ignore else */
     if (!this.options.enabled) {
       debug(yellow('Addon disabled. Disable and remove service worker...'));
 
@@ -92,6 +95,7 @@ class BroccoliWorkbox extends Plugin {
     );
 
     // Remove workbox libraries directory to prevent exception on recopying it.
+    /* istanbul ignore else */
     if (
       !workboxOptions.importWorkboxFromCDN &&
       fs.existsSync(workboxDirectory)
@@ -111,7 +115,7 @@ class BroccoliWorkbox extends Plugin {
     );
 
     workboxOptions.importScripts = filesToIncludeInSW;
-
+    /* istanbul ignore else */
     if (this.options.importScriptsTransform) {
       workboxOptions.importScripts = this.options.importScriptsTransform(
         workboxOptions.importScripts
diff --git a/tests/acceptance/simple-test.js b/tests/acceptance/simple-test.js
index dfc7f89..5f3d544 100755
--- a/tests/acceptance/simple-test.js
+++ b/tests/acceptance/simple-test.js
@@ -1,5 +1,6 @@
 import { module, test } from 'qunit';
 import { setupApplicationTest } from 'ember-qunit';
+import sinon from 'sinon';
 
 module('Acceptance | Simple Acceptance Test', (hooks) => {
   setupApplicationTest(hooks);
@@ -48,6 +49,8 @@ module('Acceptance | Simple Acceptance Test', (hooks) => {
     const registrations =
       await window.navigator.serviceWorker.getRegistrations();
 
+    console.log('ave4r si ' + JSON.stringify(registrations));
+
     assert.ok(registrations.length);
   });
 
@@ -74,6 +77,39 @@ module('Acceptance | Simple Acceptance Test', (hooks) => {
     assert.notOk(registrations.length);
   });
 
+  test('it unregisters sw but fails', async function (assert) {
+    await this.swService.register('sw.js');
+
+    const registrations = await this.swService.sw.getRegistrations();
+    const stubs = registrations.map((reg) => {
+      return sinon.stub(reg, 'unregister').callsFake(() => {
+        return Promise.resolve(false);
+      });
+    });
+
+    const stubLog = sinon.stub(this.swService, '_log');
+
+    assert.deepEqual(
+      this.events,
+      ['registrationComplete'],
+      'Event triggered: registrationComplete'
+    );
+
+    await this.swService.unregisterAll();
+
+    assert.ok(stubLog.called);
+    assert.ok(registrations.length);
+
+    assert.deepEqual(
+      this.events,
+      ['registrationComplete', 'unregistrationComplete'],
+      'Service worker does not exists'
+    );
+
+    stubs.forEach((stubReg) => stubReg.restore());
+    stubLog.restore();
+  });
+
   test.skip('it triggers "update" event on sw response', async function (assert) {
     const _reload = window.location.reload;
     let called = 0;