Going back to the point that MDS made, although most aircraft carry dual comms this does not mean that RT failure won't happen.
Whilst training another controller some years ago (but not that many!) I posed the question of my u/t if an inbound aircraft that we were watching but not yet working went RT fail - what would he expect it to do?
My u/t effectively declined to answer claiming that aircraft carry so much redundancy that it just won't happen. It was only meant as a discussion point to chat about the possible options - I didn't have a definitive answer.
Strangely, before the week was out, an inbound aircraft (a BA11, admittedly in corporate configuration but, presumably, with a similar fit to many aircraft flying around with cattle class seating) stopped talking to anyone. The first indication was when airways called to ask if we were talking to it as it was coming up to the usual handover point and they could get no response. The aircraft eventually called as it approached the overhead using a handheld radio that one of the crew carried in his bag.
The problem - a cup of coffee knocked over the comms stack.
Sadly my u/t wasn't there to eat his words.
In practice I did as Ondrej says, kept everything else out of the way and watched carefully. Chatting to the crew afterwards, I recall they were trying to follow the R/T fail procedure (but having trouble confirming that it was the 'right' one) and were uncomfortable doing so but grateful that it was generally VMC.
It brought it home that, even these days, RT failure can still happen.