Use babel polyfill in karma

package.json

@@ -35,6 +35,7 @@
     "whatwg-fetch": "^2.0.3"
   },
   "devDependencies": {
+    "@babel/polyfill": "^7.0.0",
     "@vue/test-utils": "^1.0.0-beta.26",
     "autoprefixer": "^6.4.0",
     "babel-core": "^6.0.0",

src/services/user_profile_link_generator/user_profile_link_generator.js

@@ -5,6 +5,6 @@ const generateProfileLink = (id, screenName) => {
   }
 }
 
-const isExternal = screenName => (screenName.indexOf('@') > -1)
+const isExternal = screenName => screenName.includes('@')
 
 export default generateProfileLink

test/unit/karma.conf.js

@@ -56,7 +56,10 @@ module.exports = function (config) {
     browsers: ['PhantomJS'],
     frameworks: ['mocha', 'sinon-chai'],
     reporters: ['mocha'],
-    files: ['./index.js'],
+    files: [
+      '../../node_modules/@babel/polyfill/dist/polyfill.js',
+      './index.js'
+    ],
     preprocessors: {
       './index.js': ['webpack', 'sourcemap']
     },

yarn.lock

@@ -9,6 +9,14 @@
   dependencies:
     "@babel/types" "^7.0.0"
 
+"@babel/polyfill@^7.0.0":
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/@babel/polyfill/-/polyfill-7.0.0.tgz#c8ff65c9ec3be6a1ba10113ebd40e8750fb90bff"
+  integrity sha512-dnrMRkyyr74CRelJwvgnnSUDh2ge2NCTyHVwpOdvRMHtJUyxLtMAfhBN3s64pY41zdw0kgiLPh6S20eb1NcX6Q==
+  dependencies:
+    core-js "^2.5.7"
+    regenerator-runtime "^0.11.1"
+
 "@babel/types@^7.0.0", "@babel/types@^7.0.0-beta.49":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/types/-/types-7.2.0.tgz#7941c5b2d8060e06f9601d6be7c223eef906d5d8"
@@ -1583,7 +1591,7 @@ cookie@0.3.1:
   version "0.3.1"
   resolved "https://registry.yarnpkg.com/cookie/-/cookie-0.3.1.tgz#e7e0a1f9ef43b4c8ba925c5c5a96e806d16873bb"
 
-core-js@^2.2.0:
+core-js@^2.2.0, core-js@^2.5.7:
   version "2.6.0"
   resolved "https://registry.yarnpkg.com/core-js/-/core-js-2.6.0.tgz#1e30793e9ee5782b307e37ffa22da0eacddd84d4"
   integrity sha512-kLRC6ncVpuEW/1kwrOXYX6KQASCVtrh1gQr/UiaVgFlf9WE5Vp+lNe5+h3LuMr5PAucWnnEXwH0nQHRH/gpGtw==
@@ -5510,6 +5518,11 @@ regenerator-runtime@^0.11.0:
   version "0.11.0"
   resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.11.0.tgz#7e54fe5b5ccd5d6624ea6255c3473be090b802e1"
 
+regenerator-runtime@^0.11.1:
+  version "0.11.1"
+  resolved "https://registry.yarnpkg.com/regenerator-runtime/-/regenerator-runtime-0.11.1.tgz#be05ad7f9bf7d22e056f9726cee5017fbf19e2e9"
+  integrity sha512-MguG95oij0fC3QV3URf4V2SDYGJhJnJGqvIIgdECeODCT98wSWDAJ94SSuVpYQUoTcGUIL6L4yNB7j1DFFHSBg==
+
 regenerator-transform@^0.10.0:
   version "0.10.1"
   resolved "https://registry.yarnpkg.com/regenerator-transform/-/regenerator-transform-0.10.1.tgz#1e4996837231da8b7f3cf4114d71b5691a0680dd"