code: public function renderFormAction($id, Request $request)
      {
          $em = $this->getDoctrine()->getManager();
  
          $entity = $em->getRepository('ChillCustomFieldsBundle:CustomFieldsGroup')->find($id);
      
          if (!$entity) {
              throw $this->createNotFoundException('Unable to find CustomFieldsGroups entity.');
          }
      
          $form = $this->createForm('custom_field', null, array('group' => $entity));
          $form->add('submit_dump', 'submit', array('label' => 'POST AND DUMP'));
          $form->add('submit_render','submit', array('label' => 'POST AND RENDER'));
          $form->handleRequest($request);
          
          $this->get('twig.loader')
          ->addPath(__DIR__.'/../Tests/Fixtures/App/app/Resources/views/',
              $namespace = 'test');
          
          if ($form->isSubmitted()) {
              if ($form->get('submit_render')->isClicked()) {
                  return $this->render('ChillCustomFieldsBundle:CustomFieldsGroup:render_for_test.html.twig', array(
                      'fields' => $form->getData(),
                      'customFieldsGroup' => $entity
                  ));
              }
              
              var_dump($form->getData());
              var_dump(json_enccode($form->getData()));
          }
      
          
      
          return $this
              ->render('@test/CustomField/simple_form_render.html.twig', array(
                  'form' => $form->createView()
          ));
      
      }
docs: This function render the customFieldsGroup as a form.
  
  This function is for testing purpose !
  
  The route which call this action is not in Resources/config/routing.yml,
  but in Tests/Fixtures/App/app/config.yml
  
  @param int $id