Merge pull request #12243 from edx/usman/tnl4416-spec-nesting

When using RequireJS load spec files one by one.

common/static/common/js/spec/main_requirejs.js

@@ -178,7 +178,7 @@
         testFiles[i] = '/base/' + testFiles[i];
     }
 
-    require(testFiles, function () {
+    window.requireSerial(testFiles, function () {
         // start test run, once Require.js is done
         window.__karma__.start();
     });

common/static/common/js/utils/require-serial.js

@@ -0,0 +1,23 @@
+/*
+Helper function used to require files serially instead of concurrently.
+ */
+(function (window, require) {
+  'use strict';
+
+  var requireModules = function (paths, callback, modules) {
+      // If all the modules have been loaded, call the callback.
+      if (paths.length === 0) {
+        return callback.apply(null, modules);
+      }
+      // Otherwise load the next one.
+      require([paths.shift()], function(module) {
+        modules.push(module);
+        requireModules(paths, callback, modules);
+      });
+  };
+
+  window.requireSerial = function(paths, callback) {
+    requireModules(paths, callback, []);
+  };
+
+}).call(this, window, require || RequireJS.require);

common/static/karma_common_requirejs.conf.js

@@ -46,7 +46,8 @@ var libraryFiles = [
     {pattern: 'js/test/i18n.js', included: false},
     {pattern: 'coffee/src/jquery.immediateDescendents.js', included: false},
     {pattern: 'js/vendor/requirejs/text.js', included: false},
-    {pattern: 'js/vendor/sinon-1.17.0.js', included: false}
+    {pattern: 'js/vendor/sinon-1.17.0.js', included: false},
+    {pattern: 'common/js/utils/require-serial.js', included: true}
 ];
 
 // Paths to source JavaScript files