Index: core/misc/tests/drupal.test.js
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/misc/tests/drupal.test.js	(date 1478036695000)
+++ core/misc/tests/drupal.test.js	(date 1478036695000)
@@ -0,0 +1,14 @@
+const assert = require('assert');
+domready = function () {};
+Drupal = {};
+const _ = require('../drupal.es6');
+
+describe('Drupal', function () {
+  describe('#checkPlain()', function () {
+    it('should escape html strings safe for printing', function () {
+      const html = '<span class="music">Rock & roll</span>';
+      const escaped = '&lt;span class=&quot;music&quot;&gt;Rock &amp; roll&lt;/span&gt;';
+      assert.strictEqual(Drupal.checkPlain(html), escaped, 'Drupal.checkPlain escape HTML strings');
+    });
+  });
+});
Index: core/package.json
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- core/package.json	(date 1478010521000)
+++ core/package.json	(date 1478036695000)
@@ -6,18 +6,31 @@
   "scripts": {
     "build:js": "node ./scripts/js/babel-es6-build.js",
     "watch:js": "node ./scripts/js/babel-es6-watch.js",
-    "lint:js": "eslint . --ext=.es6.js || exit 0"
+    "lint:js": "eslint . --ext=.es6.js || exit 0",
+    "test:core": "nyc mocha -r jsdom-global/register `find ./misc -name '*.test.js'` || exit 0"
   },
   "devDependencies": {
     "babel-core": "6.17.0",
     "babel-preset-es2015": "6.16.0",
     "chokidar": "1.6.0",
     "eslint": "3.8.1",
-    "glob": "^7.1.1"
+    "glob": "^7.1.1",
+    "jsdom": "9.8.3",
+    "jsdom-global": "2.1.0",
+    "mocha": "3.1.2",
+    "nyc": "^8.3.2"
   },
   "babel": {
     "presets": [
       "es2015"
+    ],
+    "plugins": [
+      [
+        "transform-object-rest-spread",
+        {
+          "useBuiltIns": true
+        }
+      ]
     ]
   }
 }