public static function assert_response_xml($status_code = 200)
{
if ($status_code !== false) {
self::assert_response_status_code($status_code);
}
// Any output before the xml opening means there was an error
$content = self::$client->getResponse()->getContent();
self::assertNotContains('[phpBB Debug]', $content);
self::assertStringStartsWith('<?xml', trim($content), 'Output found before XML specification.');
}