Added tests for hidden jump to button

app/assets/javascripts/diff_notes/components/jump_to_discussion.js.es6

@@ -17,7 +17,7 @@
         return Object.keys(this.discussions).length;
       },
       showButton: function () {
-        return this.discussionsCount > 1 || !this.discussionId;
+        return this.discussionsCount > 0 && (this.discussionsCount > 1 || !this.discussionId);
       }
     },
     methods: {

app/assets/javascripts/diff_notes/components/resolve_btn.js.es6

@@ -71,6 +71,8 @@
             CommentsStore.update(this.discussionId, this.noteId, !this.isResolved, user);
 
             ResolveService.updateUpdatedHtml(this.discussionId, data);
+          } else {
+            new Flash('An error occurred when trying to resolve a comment. Please try again.', 'alert');
           }
 
           this.$nextTick(this.updateTooltip);

app/assets/javascripts/diff_notes/services/resolve.js.es6

@@ -45,12 +45,16 @@
         mergeRequestId,
         discussionId
       }, {}).then((response) => {
+        if (response.status === 200) {
           const data = response.data;
           const user = data ? data.resolved_by : null;
           discussion.resolveAllNotes(user);
           discussion.loading = false;
 
           this.updateUpdatedHtml(discussionId, data);
+        } else {
+          new Flash('An error occurred when trying to resolve a discussion. Please try again.', 'alert');
+        }
       });
     }
 
@@ -66,11 +70,15 @@
         mergeRequestId,
         discussionId
       }, {}).then((response) => {
+        if (response.status === 200) {
           const data = response.data;
           discussion.unResolveAllNotes();
           discussion.loading = false;
 
           this.updateUpdatedHtml(discussionId, data);
+        } else {
+          new Flash('An error occurred when trying to unresolve a discussion. Please try again.', 'alert');
+        }
       });
     }
 

spec/features/merge_requests/diff_notes_resolve_spec.rb

@@ -16,6 +16,20 @@ feature 'Diff notes resolve', feature: true, js: true do
     )
   end
 
+  context 'no discussions' do
+    before do
+      project.team << [user, :master]
+      login_as user
+      note.destroy
+      visit_merge_request
+    end
+
+    it 'displays no discussion resolved data' do
+      expect(page).not_to have_content('discussion resolved')
+      expect(page).not_to have_selector('.discussion-next-btn')
+    end
+  end
+
   context 'as authorized user' do
     before do
       project.team << [user, :master]