Doctrine subquery in symfony

Question

I've got a little issue. I've got to do a query that is based on a subquery. The SQL query I need to get to is:

FROM testing t
WHERE t.id NOT IN (
    SELECT h.task_id
    FROM task t
    INNER JOIN hardware h ON h.task_id = t.id
          );

What I have for a moment is the basic query and I don't really understand how to do that subquery..

$test->createQueryBuilder('t')
            ->select('t.id')
            ->getQuery()->getArrayResult();