fix(e2e): screenshot changes will display proper error message

closes #191
closes #192

Closes #194

e2e/_screenshot.js

@@ -58,14 +58,14 @@ class Screenshot {
       let referenceScreenshot = mapnik.Image.open(this.path);
       this.overwriteExistingScreenshot();
       if (referenceScreenshot.compare(this.png)) {
-        throw new Error(`screenshot "${this.id}" has changed.`);
+        throw `screenshot "${this.id}" has changed.`;
       } else {
         console.info('[STATUS] Screenshot has not changed');
       }
     } catch (e) {
-      console.info(`[STATUS] No reference screenshot found`);
+      console.error(`[ERROR] `, e);
       this.overwriteExistingScreenshot();
-      throw new Error(`screenshot "${this.id}" was not found.`);
+      throw e;
     }
   }
 

e2e/index.e2e.js

@@ -5,7 +5,7 @@ describe('hello, protractor', function () {
     browser.get('/');
     it('should have a title', function () {
       expect(browser.getTitle()).toBe('Material2');
-      screenshot('initial state');
+      screenshot('demo page: index');
     });
   });
 });

screenshots/demo page: index.screenshot.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:606958be9d1e0ec1cc3b5e361feee28d0b1bf52b0008c8afb0f03b21a5353a9e
+size 23924

screenshots/initial state.screenshot.png

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:ba69049fdfdcffda020560f862c301494783d79ae13dc2befc377d679402b152
-size 22610