public function testReturnButtonLoaded()
 {
     $handle_15 = 'dhlonlineretoure_button_return_15';
     $handle_16 = 'dhlonlineretoure_button_return_16';
     /* @var $observer Dhl_OnlineRetoure_Model_Observer */
     $observer = Mage::getModel('dhlonlineretoure/observer');
     $action = new Varien_Object();
     $action->setFullActionName('sales_order_view');
     $event = new Varien_Event(array('action' => $action, 'layout' => Mage::getSingleton('core/layout')));
     $eventObserver = new Varien_Event_Observer();
     $eventObserver->setEvent($event);
     $observer->addReturnButtonHandle($eventObserver);
     $handles = $eventObserver->getEvent()->getLayout()->getUpdate()->getHandles();
     if (version_compare(Mage::getVersion(), '1.6.0.0', '<')) {
         $this->assertContains($handle_15, $handles);
     } else {
         $this->assertContains($handle_16, $handles);
     }
 }