Hello!
When course are not given during an academic year (as it will happen for GT next year) we still provide one exam possibility per year. If there is interest the studentexpedition can organize more if needed (bt keep in mind that if you enroll and do not show up it cost the department money, so do not misuse this privilege or it will be taken away)
In any case, if you want an exam already in August (sorry, I will not wrtie one before that) write to them and try to discuss with them the week in which you want the exam.
With my best regards
Sofia