/**
* Returns a stable instance based on $wgCirrusSearchUserTesting
* global configuration.
*
* @var callable|null $callback
* @return self
*/
public static function getInstance($callback = null)
{
global $wgCirrusSearchUserTesting;
if (self::$instance === null) {
self::$instance = new self($wgCirrusSearchUserTesting, $callback);
}
return self::$instance;
}
/**
* Unit test only
*/
public static function resetInstance()
{
self::$instance = null;
}