diff --git a/app/assets/javascripts/sidebar/components/assignees/sidebar_assignees.js b/app/assets/javascripts/sidebar/components/assignees/sidebar_assignees.js
index 74c17bc14a2..9e47039d920 100644
--- a/app/assets/javascripts/sidebar/components/assignees/sidebar_assignees.js
+++ b/app/assets/javascripts/sidebar/components/assignees/sidebar_assignees.js
@@ -1,22 +1,32 @@
 import Flash from '../../../flash';
 import AssigneeTitle from './assignee_title';
 import Assignees from './assignees';
-
 import Store from '../../stores/sidebar_store';
-import Mediator from '../../sidebar_mediator';
-
 import eventHub from '../../event_hub';
 
 export default {
   name: 'SidebarAssignees',
   data() {
     return {
-      mediator: new Mediator(),
       store: new Store(),
       loading: false,
-      field: '',
     };
   },
+  props: {
+    mediator: {
+      type: Object,
+      required: true,
+    },
+    field: {
+      type: String,
+      required: true,
+    },
+    signedIn: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+  },
   components: {
     'assignee-title': AssigneeTitle,
     assignees: Assignees,
@@ -61,10 +71,6 @@ export default {
     eventHub.$off('sidebar.removeAllAssignees', this.removeAllAssignees);
     eventHub.$off('sidebar.saveAssignees', this.saveAssignees);
   },
-  beforeMount() {
-    this.field = this.$el.dataset.field;
-    this.signedIn = typeof this.$el.dataset.signedIn !== 'undefined';
-  },
   template: `
     <div>
       <assignee-title
diff --git a/app/assets/javascripts/sidebar/components/participants/sidebar_participants.vue b/app/assets/javascripts/sidebar/components/participants/sidebar_participants.vue
index c1296b28db7..6fcd2f95309 100644
--- a/app/assets/javascripts/sidebar/components/participants/sidebar_participants.vue
+++ b/app/assets/javascripts/sidebar/components/participants/sidebar_participants.vue
@@ -1,15 +1,19 @@
 <script>
 import Store from '../../stores/sidebar_store';
-import Mediator from '../../sidebar_mediator';
 import participants from './participants.vue';
 
 export default {
   data() {
     return {
-      mediator: new Mediator(),
       store: new Store(),
     };
   },
+  props: {
+    mediator: {
+      type: Object,
+      required: true,
+    },
+  },
   components: {
     participants,
   },
@@ -21,6 +25,7 @@ export default {
     <participants
       :loading="store.isFetching.participants"
       :participants="store.participants"
-      :number-of-less-participants="7" />
+      :number-of-less-participants="7"
+    />
   </div>
 </template>
diff --git a/app/assets/javascripts/sidebar/components/subscriptions/sidebar_subscriptions.vue b/app/assets/javascripts/sidebar/components/subscriptions/sidebar_subscriptions.vue
index 25acc099699..f4bae1d3dd5 100644
--- a/app/assets/javascripts/sidebar/components/subscriptions/sidebar_subscriptions.vue
+++ b/app/assets/javascripts/sidebar/components/subscriptions/sidebar_subscriptions.vue
@@ -1,6 +1,5 @@
 <script>
 import Store from '../../stores/sidebar_store';
-import Mediator from '../../sidebar_mediator';
 import eventHub from '../../event_hub';
 import Flash from '../../../flash';
 import { __ } from '../../../locale';
@@ -9,11 +8,15 @@ import subscriptions from './subscriptions.vue';
 export default {
   data() {
     return {
-      mediator: new Mediator(),
       store: new Store(),
     };
   },
-
+  props: {
+    mediator: {
+      type: Object,
+      required: true,
+    },
+  },
   components: {
     subscriptions,
   },
diff --git a/app/assets/javascripts/sidebar/mount_sidebar.js b/app/assets/javascripts/sidebar/mount_sidebar.js
index 4032f156b15..56cc78ca0ca 100644
--- a/app/assets/javascripts/sidebar/mount_sidebar.js
+++ b/app/assets/javascripts/sidebar/mount_sidebar.js
@@ -10,6 +10,27 @@ import Translate from '../vue_shared/translate';
 
 Vue.use(Translate);
 
+function mountAssigneesComponent(mediator) {
+  const el = document.getElementById('js-vue-sidebar-assignees');
+
+  if (!el) return;
+
+  // eslint-disable-next-line no-new
+  new Vue({
+    el,
+    components: {
+      SidebarAssignees,
+    },
+    render: createElement => createElement('sidebar-assignees', {
+      props: {
+        mediator,
+        field: el.dataset.field,
+        signedIn: el.hasAttribute('data-signed-in'),
+      },
+    }),
+  });
+}
+
 function mountConfidentialComponent(mediator) {
   const el = document.getElementById('js-confidential-entry-point');
 
@@ -49,9 +70,10 @@ function mountLockComponent(mediator) {
   }).$mount(el);
 }
 
-function mountParticipantsComponent() {
+function mountParticipantsComponent(mediator) {
   const el = document.querySelector('.js-sidebar-participants-entry-point');
 
+  // eslint-disable-next-line no-new
   if (!el) return;
 
   // eslint-disable-next-line no-new
@@ -60,11 +82,15 @@ function mountParticipantsComponent() {
     components: {
       sidebarParticipants,
     },
-    render: createElement => createElement('sidebar-participants', {}),
+    render: createElement => createElement('sidebar-participants', {
+      props: {
+        mediator,
+      },
+    }),
   });
 }
 
-function mountSubscriptionsComponent() {
+function mountSubscriptionsComponent(mediator) {
   const el = document.querySelector('.js-sidebar-subscriptions-entry-point');
 
   if (!el) return;
@@ -75,22 +101,35 @@ function mountSubscriptionsComponent() {
     components: {
       sidebarSubscriptions,
     },
-    render: createElement => createElement('sidebar-subscriptions', {}),
+    render: createElement => createElement('sidebar-subscriptions', {
+      props: {
+        mediator,
+      },
+    }),
   });
 }
 
-function mount(mediator) {
-  const sidebarAssigneesEl = document.getElementById('js-vue-sidebar-assignees');
-  // Only create the sidebarAssignees vue app if it is found in the DOM
-  // We currently do not use sidebarAssignees for the MR page
-  if (sidebarAssigneesEl) {
-    new Vue(SidebarAssignees).$mount(sidebarAssigneesEl);
-  }
+function mountTimeTrackingComponent() {
+  const el = document.getElementById('issuable-time-tracker');
 
+  if (!el) return;
+
+  // eslint-disable-next-line no-new
+  new Vue({
+    el,
+    components: {
+      SidebarTimeTracking,
+    },
+    render: createElement => createElement('sidebar-time-tracking', {}),
+  });
+}
+
+export function mountSidebar(mediator) {
+  mountAssigneesComponent(mediator);
   mountConfidentialComponent(mediator);
   mountLockComponent(mediator);
-  mountParticipantsComponent();
-  mountSubscriptionsComponent();
+  mountParticipantsComponent(mediator);
+  mountSubscriptionsComponent(mediator);
 
   new SidebarMoveIssue(
     mediator,
@@ -98,7 +137,9 @@ function mount(mediator) {
     $('.js-move-issue-confirmation-button'),
   ).init();
 
-  new Vue(SidebarTimeTracking).$mount('#issuable-time-tracker');
+  mountTimeTrackingComponent();
 }
 
-export default mount;
+export function getSidebarOptions() {
+  return JSON.parse(document.querySelector('.js-sidebar-options').innerHTML);
+}
diff --git a/app/assets/javascripts/sidebar/sidebar_bundle.js b/app/assets/javascripts/sidebar/sidebar_bundle.js
index f78287e504b..04c39d7b6b5 100644
--- a/app/assets/javascripts/sidebar/sidebar_bundle.js
+++ b/app/assets/javascripts/sidebar/sidebar_bundle.js
@@ -1,9 +1,8 @@
 import Mediator from './sidebar_mediator';
-import mountSidebar from './mount_sidebar';
+import { mountSidebar, getSidebarOptions } from './mount_sidebar';
 
 function domContentLoaded() {
-  const sidebarOptions = JSON.parse(document.querySelector('.js-sidebar-options').innerHTML);
-  const mediator = new Mediator(sidebarOptions);
+  const mediator = new Mediator(getSidebarOptions());
   mediator.fetch();
 
   mountSidebar(mediator);
diff --git a/app/assets/javascripts/sidebar/sidebar_mediator.js b/app/assets/javascripts/sidebar/sidebar_mediator.js
index ed7ab09be06..d86557e870a 100644
--- a/app/assets/javascripts/sidebar/sidebar_mediator.js
+++ b/app/assets/javascripts/sidebar/sidebar_mediator.js
@@ -8,7 +8,6 @@ export default class SidebarMediator {
     if (!SidebarMediator.singleton) {
       this.initSingleton(options);
     }
-
     return SidebarMediator.singleton;
   }
 
diff --git a/app/assets/javascripts/sidebar/stores/sidebar_store.js b/app/assets/javascripts/sidebar/stores/sidebar_store.js
index 73eb25e2333..f20cc6d8cca 100644
--- a/app/assets/javascripts/sidebar/stores/sidebar_store.js
+++ b/app/assets/javascripts/sidebar/stores/sidebar_store.js
@@ -1,33 +1,37 @@
 export default class SidebarStore {
-  constructor(store) {
+  constructor(options) {
     if (!SidebarStore.singleton) {
-      const { currentUser, rootPath, editable } = store;
-      this.currentUser = currentUser;
-      this.rootPath = rootPath;
-      this.editable = editable;
-      this.timeEstimate = 0;
-      this.totalTimeSpent = 0;
-      this.humanTimeEstimate = '';
-      this.humanTimeSpent = '';
-      this.assignees = [];
-      this.isFetching = {
-        assignees: true,
-        participants: true,
-        subscriptions: true,
-      };
-      this.isLoading = {};
-      this.autocompleteProjects = [];
-      this.moveToProjectId = 0;
-      this.isLockDialogOpen = false;
-      this.participants = [];
-      this.subscribed = null;
-
-      SidebarStore.singleton = this;
+      this.initSingleton(options);
     }
 
     return SidebarStore.singleton;
   }
 
+  initSingleton(options) {
+    const { currentUser, rootPath, editable } = options;
+    this.currentUser = currentUser;
+    this.rootPath = rootPath;
+    this.editable = editable;
+    this.timeEstimate = 0;
+    this.totalTimeSpent = 0;
+    this.humanTimeEstimate = '';
+    this.humanTimeSpent = '';
+    this.assignees = [];
+    this.isFetching = {
+      assignees: true,
+      participants: true,
+      subscriptions: true,
+    };
+    this.isLoading = {};
+    this.autocompleteProjects = [];
+    this.moveToProjectId = 0;
+    this.isLockDialogOpen = false;
+    this.participants = [];
+    this.subscribed = null;
+
+    SidebarStore.singleton = this;
+  }
+
   setAssigneeData(data) {
     this.isFetching.assignees = false;
     if (data.assignees) {
diff --git a/app/assets/stylesheets/framework/sidebar.scss b/app/assets/stylesheets/framework/sidebar.scss
index 792981fdc48..3ebba4f9efb 100644
--- a/app/assets/stylesheets/framework/sidebar.scss
+++ b/app/assets/stylesheets/framework/sidebar.scss
@@ -50,6 +50,11 @@
     &:not(.disabled) {
       cursor: pointer;
     }
+
+    svg {
+      width: $gl-padding;
+      height: $gl-padding;
+    }
   }
 }
 
diff --git a/app/assets/stylesheets/pages/issuable.scss b/app/assets/stylesheets/pages/issuable.scss
index 32f2fa88236..2e26f2b5bbd 100644
--- a/app/assets/stylesheets/pages/issuable.scss
+++ b/app/assets/stylesheets/pages/issuable.scss
@@ -470,7 +470,8 @@
       }
     }
 
-    .milestone-title span {
+    .milestone-title span,
+    .collapse-truncated-title {
       @include str-truncated(100%);
       display: block;
       margin: 0 4px;
diff --git a/spec/javascripts/sidebar/sidebar_assignees_spec.js b/spec/javascripts/sidebar/sidebar_assignees_spec.js
index 929ba75e67d..b97e24d9dcf 100644
--- a/spec/javascripts/sidebar/sidebar_assignees_spec.js
+++ b/spec/javascripts/sidebar/sidebar_assignees_spec.js
@@ -4,20 +4,29 @@ import SidebarMediator from '~/sidebar/sidebar_mediator';
 import SidebarService from '~/sidebar/services/sidebar_service';
 import SidebarStore from '~/sidebar/stores/sidebar_store';
 import Mock from './mock_data';
+import mountComponent from '../helpers/vue_mount_component_helper';
 
 describe('sidebar assignees', () => {
-  let component;
-  let SidebarAssigneeComponent;
+  let vm;
+  let mediator;
+  let sidebarAssigneesEl;
   preloadFixtures('issues/open-issue.html.raw');
 
   beforeEach(() => {
     Vue.http.interceptors.push(Mock.sidebarMockInterceptor);
-    SidebarAssigneeComponent = Vue.extend(SidebarAssignees);
-    spyOn(SidebarMediator.prototype, 'saveAssignees').and.callThrough();
-    spyOn(SidebarMediator.prototype, 'assignYourself').and.callThrough();
-    this.mediator = new SidebarMediator(Mock.mediator);
+
     loadFixtures('issues/open-issue.html.raw');
-    this.sidebarAssigneesEl = document.querySelector('#js-vue-sidebar-assignees');
+
+    mediator = new SidebarMediator(Mock.mediator);
+    spyOn(mediator, 'saveAssignees').and.callThrough();
+    spyOn(mediator, 'assignYourself').and.callThrough();
+
+    const SidebarAssigneeComponent = Vue.extend(SidebarAssignees);
+    sidebarAssigneesEl = document.querySelector('#js-vue-sidebar-assignees');
+    vm = mountComponent(SidebarAssigneeComponent, {
+      mediator,
+      field: sidebarAssigneesEl.dataset.field,
+    }, sidebarAssigneesEl);
   });
 
   afterEach(() => {
@@ -28,30 +37,24 @@ describe('sidebar assignees', () => {
   });
 
   it('calls the mediator when saves the assignees', () => {
-    component = new SidebarAssigneeComponent()
-      .$mount(this.sidebarAssigneesEl);
-    component.saveAssignees();
-
-    expect(SidebarMediator.prototype.saveAssignees).toHaveBeenCalled();
+    vm.saveAssignees();
+    expect(mediator.saveAssignees).toHaveBeenCalled();
   });
 
   it('calls the mediator when "assignSelf" method is called', () => {
-    component = new SidebarAssigneeComponent()
-      .$mount(this.sidebarAssigneesEl);
-    component.assignSelf();
+    vm.assignSelf();
 
-    expect(SidebarMediator.prototype.assignYourself).toHaveBeenCalled();
-    expect(this.mediator.store.assignees.length).toEqual(1);
+    expect(mediator.assignYourself).toHaveBeenCalled();
+    expect(mediator.store.assignees.length).toEqual(1);
   });
 
   it('hides assignees until fetched', (done) => {
-    component = new SidebarAssigneeComponent().$mount(this.sidebarAssigneesEl);
-    const currentAssignee = this.sidebarAssigneesEl.querySelector('.value');
+    const currentAssignee = sidebarAssigneesEl.querySelector('.value');
     expect(currentAssignee).toBe(null);
 
-    component.store.isFetching.assignees = false;
+    vm.store.isFetching.assignees = false;
     Vue.nextTick(() => {
-      expect(component.$el.querySelector('.value')).toBeVisible();
+      expect(vm.$el.querySelector('.value')).toBeVisible();
       done();
     });
   });
diff --git a/spec/javascripts/sidebar/sidebar_subscriptions_spec.js b/spec/javascripts/sidebar/sidebar_subscriptions_spec.js
index 7adf22b0f1f..a6113cb0bae 100644
--- a/spec/javascripts/sidebar/sidebar_subscriptions_spec.js
+++ b/spec/javascripts/sidebar/sidebar_subscriptions_spec.js
@@ -26,11 +26,14 @@ describe('Sidebar Subscriptions', function () {
   });
 
   it('calls the mediator toggleSubscription on event', () => {
-    spyOn(SidebarMediator.prototype, 'toggleSubscription').and.returnValue(Promise.resolve());
-    vm = mountComponent(SidebarSubscriptions, {});
+    const mediator = new SidebarMediator();
+    spyOn(mediator, 'toggleSubscription').and.returnValue(Promise.resolve());
+    vm = mountComponent(SidebarSubscriptions, {
+      mediator,
+    });
 
     eventHub.$emit('toggleSubscription');
 
-    expect(SidebarMediator.prototype.toggleSubscription).toHaveBeenCalled();
+    expect(mediator.toggleSubscription).toHaveBeenCalled();
   });
 });