public function testValidateHeadersFailure()
 {
     $response = new ezcWebdavOptionsResponse();
     $response->setHeader('DAV', null);
     try {
         $response->validateHeaders();
         $this->fail("Exception not thrown on missing header 'DAV'.");
     } catch (ezcWebdavMissingHeaderException $e) {
     }
     $response->setHeader('DAV', '1, 2#extended');
     try {
         $response->validateHeaders();
         $this->fail("Exception not thrown on invalid header 'DAV'.");
     } catch (ezcWebdavInvalidHeaderException $e) {
     }
 }