test(end to end): Added function to wait for loading of specific image by srcSet attribute.

Prevents tests from running before the next image is loaded.

Author: jackhkmatthews

e2e/app.e2e-spec.ts

@@ -78,15 +78,19 @@ describe('ImageLoader Lib E2E Tests', function () {
 
       page.setWindowSize(768, 580)
         .then(() => {
-          browser.wait(() => page.getLoadedImageElement());
+          browser.wait(() => page.getLoadedImageElementBySrcSet(
+            'http://via.placeholder.com/350x250?text=md+1x 1x, http://via.placeholder.com/700x500?text=md+2x 2x'
+          ), 5000);
         });
 
       imgSrc = page.getImageElement().getAttribute('srcset');
       expect(imgSrc).toEqual('http://via.placeholder.com/350x250?text=md+1x 1x, http://via.placeholder.com/700x500?text=md+2x 2x');
 
       page.setWindowSize(1024, 580)
         .then(() => {
-          browser.wait(() => page.getLoadedImageElement());
+          browser.wait(() => page.getLoadedImageElementBySrcSet(
+            'http://via.placeholder.com/700x400?text=lg+1x 1x, http://via.placeholder.com/1400x800?text=lg+2x 2x'
+          ), 5000);
         });
 
       imgSrc = page.getImageElement().getAttribute('srcset');
@@ -105,13 +109,17 @@ describe('ImageLoader Lib E2E Tests', function () {
 
       page.setWindowSize(768, 580)
         .then(() => {
-          browser.wait(() => page.getLoadedImageElement());
+          browser.wait(() => page.getLoadedImageElementBySrcSet(
+            'http://via.placeholder.com/350x250?text=md+1x 1x, http://via.placeholder.com/700x500?text=md+2x 2x'
+          ), 5000);
         });
       expect(page.getFullResCountElement().getText()).toEqual('2');
 
       page.setWindowSize(1024, 580)
         .then(() => {
-          browser.wait(() => page.getLoadedImageElement());
+          browser.wait(() => page.getLoadedImageElementBySrcSet(
+            'http://via.placeholder.com/700x400?text=lg+1x 1x, http://via.placeholder.com/1400x800?text=lg+2x 2x'
+          ), 5000);
         });
       expect(page.getFullResCountElement().getText()).toEqual('3');
     });

e2e/app.po.ts

@@ -25,6 +25,10 @@ export class AppPage {
     return element(by.css('.sn-image-loaded')).isPresent();
   }
 
+  getLoadedImageElementBySrcSet(srcSet) {
+    return element(by.css(`img[srcSet="${srcSet}"]`)).isPresent();
+  }
+
   getplaceholderBooleanElement() {
     return element(by.css('.placeholder-boolean'));
   }