Merge branch 'leipert-make-canvas-more-tolerant' into 'master'

Make favicon tests more fault resistent

Closes #50527

See merge request gitlab-org/gitlab-ce!22686

2 files changed, 69 insertions, 10 deletions

diff --git a/spec/javascripts/lib/utils/common_utils_spec.js b/spec/javascripts/lib/utils/common_utils_spec.js
index 0dc7e93539a..121c4040212 100644
--- a/spec/javascripts/lib/utils/common_utils_spec.js
+++ b/spec/javascripts/lib/utils/common_utils_spec.js
@@ -3,6 +3,25 @@ import * as commonUtils from '~/lib/utils/common_utils';
 import MockAdapter from 'axios-mock-adapter';
 import { faviconDataUrl, overlayDataUrl, faviconWithOverlayDataUrl } from './mock_data';
 
+const PIXEL_TOLERANCE = 0.2;
+
+/**
+ * Loads a data URL as the src of an
+ * {@link https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/Image|Image}
+ * and resolves to that Image once loaded.
+ *
+ * @param url
+ * @returns {Promise}
+ */
+const urlToImage = url =>
+  new Promise(resolve => {
+    const img = new Image();
+    img.onload = function() {
+      resolve(img);
+    };
+    img.src = url;
+  });
+
 describe('common_utils', () => {
   describe('parseUrl', () => {
     it('returns an anchor tag with url', () => {
@@ -513,8 +532,9 @@ describe('common_utils', () => {
     it('should return the favicon with the overlay', done => {
       commonUtils
         .createOverlayIcon(faviconDataUrl, overlayDataUrl)
-        .then(url => {
-          expect(url).toEqual(faviconWithOverlayDataUrl);
+        .then(url => Promise.all([urlToImage(url), urlToImage(faviconWithOverlayDataUrl)]))
+        .then(([actual, expected]) => {
+          expect(actual).toImageDiffEqual(expected, PIXEL_TOLERANCE);
           done();
         })
         .catch(done.fail);
@@ -536,10 +556,10 @@ describe('common_utils', () => {
     it('should set page favicon to provided favicon overlay', done => {
       commonUtils
         .setFaviconOverlay(overlayDataUrl)
-        .then(() => {
-          expect(document.getElementById('favicon').getAttribute('href')).toEqual(
-            faviconWithOverlayDataUrl,
-          );
+        .then(() => document.getElementById('favicon').getAttribute('href'))
+        .then(url => Promise.all([urlToImage(url), urlToImage(faviconWithOverlayDataUrl)]))
+        .then(([actual, expected]) => {
+          expect(actual).toImageDiffEqual(expected, PIXEL_TOLERANCE);
           done();
         })
         .catch(done.fail);
@@ -582,10 +602,10 @@ describe('common_utils', () => {
 
       commonUtils
         .setCiStatusFavicon(BUILD_URL)
-        .then(() => {
-          const favicon = document.getElementById('favicon');
-
-          expect(favicon.getAttribute('href')).toEqual(faviconWithOverlayDataUrl);
+        .then(() => document.getElementById('favicon').getAttribute('href'))
+        .then(url => Promise.all([urlToImage(url), urlToImage(faviconWithOverlayDataUrl)]))
+        .then(([actual, expected]) => {
+          expect(actual).toImageDiffEqual(expected, PIXEL_TOLERANCE);
           done();
         })
         .catch(done.fail);
diff --git a/spec/javascripts/matchers.js b/spec/javascripts/matchers.js
index 0d465510fd3..406527b08a3 100644
--- a/spec/javascripts/matchers.js
+++ b/spec/javascripts/matchers.js
@@ -1,3 +1,5 @@
+import pixelmatch from 'pixelmatch';
+
 export default {
   toContainText: () => ({
     compare(vm, text) {
@@ -54,4 +56,41 @@ export default {
       return result;
     },
   }),
+  toImageDiffEqual: () => {
+    const getImageData = img => {
+      const canvas = document.createElement('canvas');
+      canvas.width = img.width;
+      canvas.height = img.height;
+      canvas.getContext('2d').drawImage(img, 0, 0);
+      return canvas.getContext('2d').getImageData(0, 0, img.width, img.height).data;
+    };
+
+    return {
+      compare(actual, expected, threshold = 0.1) {
+        if (actual.height !== expected.height || actual.width !== expected.width) {
+          return {
+            pass: false,
+            message: `Expected image dimensions (h x w) of ${expected.height}x${expected.width}.
+            Received an image with ${actual.height}x${actual.width}`,
+          };
+        }
+
+        const { width, height } = actual;
+        const differentPixels = pixelmatch(
+          getImageData(actual),
+          getImageData(expected),
+          null,
+          width,
+          height,
+          { threshold },
+        );
+
+        return {
+          pass: differentPixels < 20,
+          message: `${differentPixels} pixels differ more than ${threshold *
+            100} percent between input and output.`,
+        };
+      },
+    };
+  },
 };