I am testing a Form Type I defined for an application. During testing the form type, using symfony's TypeTestCase class a message "Could not load type "entity"" appears. What can I do to solve the problem??

```
class MyType extends AbstractType {
  public function buildForm(FormBuilderInterface $builder, array $options) {
    $builder->add('otherType', 'entity', array('class' => 'Bundle:OtherType'));
  }
}

class MyTypeTest extends TypeTestCase {
  public function testSth() {
    $type = new MyType();
  }
}

```