Angular Karma - Directive with isolated scope and controllerAs, calling element.isolateScope() return undefined

Hi have this directive:

angular.module('xos.uiComponents.table', [])
.directive('xosTable', function(){
  return {
    restrict: 'E',
    scope: {
      data: '=',
      config: '='
    },
    template: `
      <!-- <pre>{{vm.data | json}}</pre> -->
      <table ng-class="vm.classes" ng-show="vm.data.length > 0">
        <thead>
          <tr>
            <th ng-repeat="col in vm.columns">{{col.label}}</th>
          </tr>
        </thead>
        <tbody>
          <tr ng-repeat="item in vm.data">
            <td ng-repeat="col in vm.columns">{{item[col.prop]}}</td>
          </tr>
        </tbody>
      </table>
    `,
    bindToController: true,
    controllerAs: 'vm',
    controller: function(){

      if(!this.config){
        throw new Error('[xosTable] Please provide a configuration via the "config" attribute');
      }

      if(!this.config.columns){
        throw new Error('[xosTable] Please provide a columns list in the configuration');
      }

      this.columns = this.config.columns;
      this.classes = this.config.classes || 'table table-striped table-bordered';

    }
  }
})

And I'm trying to test it but I cannot access the isolateScope(), here is my testing code:

describe('when correctly configured', function() {
  let scope, element, is;

  beforeEach(inject(function ($compile, $rootScope) {
    scope = $rootScope.$new();

    scope.config = {
      columns: [
        {
          label: 'Label 1',
          prop: 'label-1'
        },
        {
          label: 'Label 2',
          prop: 'label-2'
        }
      ]
    };

    scope.data = [
      {
        'label-1': 'Sample 1.1',
        'label-2': 'Sample 1.2'
      },
      {
        'label-1': 'Sample 2.1',
        'label-2': 'Sample 2.2'
      }
    ]

    element = angular.element('<xos-table config="config" data="data"></xos-table>');
    $compile(element)(scope);
    is = element.isolateScope();
    scope.$digest();

  }));

  it('should contain 2 columns', function() {
    expect(is.columns).toEqual(2);
  });
});

I've this same setup a lot of times, any idea on why I cannot access the isolateScope of my directive?

Here is a Plunker with code and test: http://plnkr.co/edit/JYYtck?p=preview

You have made three mistakes in your test:

1. you didn't load the module containing the directive (it's loaded in a separate describe block). This is why the isolateScope is undefined;
2. You use scope.columns instead os scope.vm.columns;
3. You compared the columns array to 2, instead of comparing its length to 2.

Here is the fixed plunkr.

Extract:

beforeEach(module('xos.uiComponents.table'));

[...]

it('should contain 2 columns', function() {
    console.log('aaa', iso);

    // one is the filter, the other two are the products, one is the pagination
    expect(iso.vm.columns.length).toEqual(2);
});