Update image viewer test

test/src/imageviewer/widget.spec.ts

@@ -165,15 +165,13 @@ describe('ImageViewer', () => {
 
   describe('#onUpdateRequest()', () => {
 
-    it('should add the image', (done) => {
+    it('should render the image', () => {
       let img: HTMLImageElement = widget.node.querySelector('img');
-      expect(img.src).to.be('');
-      context.ready.then(() => {
+      return widget.ready.then(() => {
         MessageLoop.sendMessage(widget, Widget.Msg.UpdateRequest);
         expect(widget.methods).to.contain('onUpdateRequest');
         expect(img.src).to.contain(IMAGE.content);
-        done();
-      }).catch(done);
+      });
     });
 
   });