public function assertContainsOnlyInstancesOf($class, $haystack, $message = '{:message}')
{
$result = array();
foreach ($haystack as $key => &$value) {
if (!is_a($value, $class)) {
$result[$key] =& $value;
break;
}
}
return $this->assert(empty($result), $message, array('expected' => $class, 'result' => $result));
}