I just took my car ( 99 Nissan Almera ) in for a pre-inspection check and the mechanic said both struts have to be completely replaced because what appear to be rubber / plastic dust shields at the top of the struts are torn up ( these are called boots? ). He did not do any kind of inspection beyond just looking at the torn up boots and citing them as the reason for replacement. Local law requires the boot to be whole and in place, regardless of the condition of the strut / shock absorber.
However, the struts seem to be working fine to the extent that the car drives very smoothly and there doesn't seem to be any excessive bounce when going over speed bumps and such.
I also checked the chrome shock absorber shaft for oil, and it seemed mostly dry, with maybe a barely detectable film on it.
I did a bounce test and it went up once and settled, without too much noticeable oscillation.
Do the struts need to be completely replaced because the boot / dust shield is torn up, or can just the rubber boot be replaced?
EDIT: Instructions for replacing the shock / strut boot - so apparently it's possible, question is if it's worth it.
Here are some pictures of the two front struts: