You'll have to brush them down with a wire brush beforehand, they're not actually a fail item anyway
per se...
unless they are actually broken. but if you give them a spruce up with a wire brush and some paint , they'll not only last longer but the whole area looks like you're looking after the car in general.
Instead of trying to guess what they might fail something on, check the whole list of stuff they actually check on
https://www.gov.uk/guidance/mot-ins...ivate-passenger-and-light-commercial-vehicles
If there's visible rust/corrosion they can check its integrity, if they can't see they can't go poking about looking for trouble, unless there's a hint of visible.