Get container in test class Symfony2

how I can get container to be able getting mys services in tests classes. I found the solution to require_once dir(__FILE__). '/...../AppKernel.php;, But when I go into WebTestCase class and found

protected static function createClient(array $options = array(), array $server = array())
{
    static::bootKernel($options);

    $client = static::$kernel->getContainer()->get('test.client');
    $client->setServerParameters($server);

    return $client;
}

Where Kernel booting, and another class KernelTestCase so I want to know I need to require_once AppKernel file or there is exist some more flexible and better method to get service container? Thanks!