public static function assertContainsOnlyInstancesOf($classname, $haystack, $message = '')
{
if (!(is_array($haystack) || is_object($haystack) && $haystack instanceof Traversable)) {
throw PHPUnit_Util_InvalidArgumentHelper::factory(2, 'array or traversable');
}
static::assertThat($haystack, new PHPUnit_Framework_Constraint_TraversableContainsOnly($classname, false), $message);
}