Ensure images don't get stuck on opacity 0

js/image.spec.js

@@ -20,16 +20,38 @@ describe('Image', () => {
     expect(img.image).toBe(image);
   });
 
-  test('fadeIn should set the element opacity to 0', () => {
+  test('fadeIn should set the element opacity to 1', () => {
     const img = new Image(image);
     img.fadeIn();
+    expect(img.image.style.opacity).toBe('1');
+  });
+
+  test('start should set the element opacity to 0', () => {
+    const img = new Image(image);
+    img.start();
     expect(img.image.style.opacity).toBe('0');
   });
 
-  test('showImage should set the element opacity to 1', () => {
+  test('start should call fadeIn when image has already loaded', () => {
     const img = new Image(image);
-    img.showImage();
-    expect(img.image.style.opacity).toBe('1');
+    img.fadeIn = jest.fn();
+    Object.defineProperty(img.image, 'complete', {
+      value: true,
+      writable: false,
+    });
+    img.start();
+    expect(img.fadeIn).toHaveBeenCalledTimes(1);
+  });
+
+  test('start should call attachLoadedEvent if image has not yet loaded', () => {
+    const img = new Image(image);
+    img.attachLoadedEvent = jest.fn();
+    Object.defineProperty(img.image, 'complete', {
+      value: false,
+      writable: false,
+    });
+    img.start();
+    expect(img.attachLoadedEvent).toHaveBeenCalledTimes(1);
   });
 });