fix frontend tests

spec/javascripts/commits_spec.js.es6

 /* global CommitsList */
-//= require jquery.endless-scroll
-//= require pager
-//= require commits
+require('vendor/jquery.endless-scroll');
+require('~/pager');
+require('~/commits');
 (() => {
+  // TODO: remove this hack!
+  // PhantomJS causes spyOn to panic because replaceState isn't "writable"
+  let phantomjs;
+  try {
+    phantomjs = !Object.getOwnPropertyDescriptor(window.history, 'replaceState').writable;
+  } catch (err) {
+    phantomjs = false;
+  }
+
   describe('Commits List', () => {
     beforeEach(() => {
       setFixtures(`
@@ -25,7 +34,10 @@
       beforeEach(() => {
         CommitsList.init(25);
         CommitsList.searchField.val('');
-        spyOn(history, 'replaceState').and.stub();
+
+        if (!phantomjs) {
+          spyOn(history, 'replaceState').and.stub();
+        }
         ajaxSpy = spyOn(jQuery, 'ajax').and.callFake((req) => {
           req.success({
             data: '<li>Result</li>',

spec/javascripts/filtered_search/filtered_search_manager_spec.js.es6

 /* global Turbolinks */
-//= require turbolinks
-//= require lib/utils/common_utils
-//= require filtered_search/filtered_search_token_keys
-//= require filtered_search/filtered_search_tokenizer
-//= require filtered_search/filtered_search_dropdown_manager
-//= require filtered_search/filtered_search_manager
+require('~/lib/utils/common_utils');
+require('~/filtered_search/filtered_search_token_keys');
+require('~/filtered_search/filtered_search_tokenizer');
+require('~/filtered_search/filtered_search_dropdown_manager');
+require('~/filtered_search/filtered_search_manager');
 (() => {
   describe('Filtered Search Manager', () => {