message: Change forEach to map
diff: @@ -33,7 +33,7 @@ extendInterfaces('stub', function(context, teardown) {
  var proto = document.createElement(tagName).constructor.prototype;
  // For all keys in the implementation to stub with..
  - var stubs = Object.keys(implementation).forEach(function(key) {
  + var stubs = Object.keys(implementation).map(function(key) {
  // Stub the method on the element prototype with Sinon:
  return sinon.stub(proto, key, implementation[key]);
  });
  