Fix jest config so that it would run on Ubuntu correctly.

Author: trekhleb

Diff for: jest.config.js

@@ -21,5 +21,8 @@ module.exports = {
   // The pattern Jest uses to detect test files.
   testRegex: '(/__tests__/.*|(\\.|/)(test|spec))\\.jsx?$',
 
-  testURL: 'http://localhost/'
+  // This option sets the URL for the jsdom environment.
+  // It is reflected in properties such as location.href.
+  // @see: https://github.com/facebook/jest/issues/6769
+  testURL: 'http://localhost/',
 };