Backport PR elastic#8822

---------

**Commit 1:**
[tests] ensure that the notifier is emptied by each test

* Original sha: 11e9af0d765960bcf586bbebe2d9309b1506d264 [formerly 0cdef8c]
* Authored by spalger <[email protected]> on 2016-10-25T00:09:57Z

**Commit 2:**
[testHarness] use generic Error class

* Original sha: d7e994e720ebdb6a2c0cd499936956ad1fe1fbee [formerly 34659fb]
* Authored by spalger <[email protected]> on 2016-10-25T22:11:39Z


Former-commit-id: cfb469b

Author: elastic-jasper

src/ui/public/notify/__tests__/notifier.js

@@ -33,10 +33,13 @@ describe('Notifier', function () {
 
   beforeEach(function () {
     params = { location: 'foo' };
-    while (Notifier.prototype._notifs.pop()); // clear global notifications
     notifier = new Notifier(params);
   });
 
+  afterEach(function () {
+    Notifier.prototype._notifs.length = 0;
+  });
+
   describe('#constructor()', function () {
     it('sets #from from given location', function () {
       expect(notifier.from).to.equal(params.location);
@@ -465,13 +468,12 @@ describe('Directive Notification', function () {
       scope;
     });
 
-    while (Notifier.prototype._notifs.pop()); // clear global notifications
-
     notifier = new Notifier({ location: 'directiveFoo' });
     directiveNotification = notifier.directive(directiveParam, customParams);
   });
 
   afterEach(() => {
+    Notifier.prototype._notifs.length = 0;
     directiveNotification.clear();
     scope.$destroy();
   });

src/ui/public/route_based_notifier/__tests__/index.js

@@ -10,12 +10,15 @@ describe('ui/route_based_notifier', function () {
 
   beforeEach(ngMock.module('kibana'));
   beforeEach(ngMock.inject(($injector) => {
-    remove(Notifier.prototype._notifs); // hack to reset the global notification array
     const Private = $injector.get('Private');
     routeBasedNotifier = Private(routeBasedNotifierProvider);
     $rootScope = $injector.get('$rootScope');
   }));
 
+  afterEach(() => {
+    Notifier.prototype._notifs.length = 0;
+  });
+
   describe('#warning()', () => {
     it('adds a warning notification', () => {
       routeBasedNotifier.warning('wat');

src/ui/public/test_harness/test_harness.js

@@ -6,6 +6,7 @@ import chrome from 'ui/chrome';
 import Nonsense from 'Nonsense';
 import sinon from 'sinon';
 import _ from 'lodash';
+import Notifier from 'ui/notify/notifier';
 
 import StackTraceMapper from 'ui/stack_trace_mapper';
 import { parse } from 'url';
@@ -55,6 +56,13 @@ before(function () {
   sinon.useFakeXMLHttpRequest();
 });
 
+beforeEach(function () {
+  if (Notifier.prototype._notifs.length) {
+    Notifier.prototype._notifs.length = 0;
+    throw new Error('notifications were left in the notifier');
+  }
+});
+
 
 /*** Kick off mocha, called at the end of test entry files ***/
 exports.bootstrap = function () {