title: Karma testing: TypeError: Attempted to assign to readonly property
body: <p>When I am trying to unit test my controller I am getting the error.When I debug the testcase's expect I am getting the expected value but its failing with below error.What am I missing here or whether I am testing the controller variable in a wrong manner? </p>
  
  <p>My spec file is below</p>
  
  <pre><code>'use strict';
  describe('Information.controller', function () {
  beforeEach(angular.mock.module('asp'));
  var InformationController, scope;
  
  beforeEach(inject(function($controller, $rootScope) {
      scope = $rootScope.$new();
      InformationController = $controller('InformationController', {
          $scope: scope
      });
  }));
  
  fit('Should remove the object without info from the  object', function () {
      InformationController.Data = [
          {
              "ban": "03745645455",
              "accountNo": "0000drgyt456456565",
              "id": "2c4cc5e8-f360367"
          },
          {
              "ban": "27346fgh9080",
              "accountNo": "000456456ytr655680",
              "id": "2c4cc8ae-50bbf360367"
          }
      ];
      InformationController.banList = InformationController.Data.map((value, index) =&gt; (value &amp;&amp; value.ban ? {'id': index, 'text': value.ban} : null))
      .filter(value =&gt; value);
      expect(InformationController.banList.length).toBe(3);
  });
  });
  </code></pre>