Thanks
@Peskyjones @lukemk5gti ir looks fine to me as they all do this. If it fails it will usually seize and not vibrate iirc as never had or seen one lose its tension tbh.
To test it you will require a 15mm spanner as long as possible for ease of use which will fit on the top of the tensioner and pull back towards you. best to remove the belt but you may struggle to get it back on.
I've been able to hold the belt off the alternator pulley whilst I check the tensioner with the left hand and refit the belt without it dropping off the other pulleys and thinking *oh sugar* what just happened there
Hope that helps