There are several different 'generic' types of test pilot: experimental, service and production, as examples.
I am assuming that you refer to the service TP who has graduated from ETPS or another appropriate test flying academy.
Service TPs - according to the plot - undertake test flying within the flight envelope, already opened by the experimental TPs. The tasks they perform are, therefore, very wide and can vary from fairly straight forward tasks eg to clear a piece of equipment for in-service use, through to the acceptance of a new aircraft type into the service and to lead on all the work that entails.
TPs are not employed exclusively on testing work and might reasonably expect to have a balanced career, which may include returning to test flying perhaps in a more senior capacity. They are, of course, an attractive target for industry and might be loaned to a manufacturer or leave the service and join a company. Of course their TP training, which develops - inter alia - their analytical skills and extends their flying experience, is useful in all sorts of roles.
Why not canvas this forum for a TP? On the promise of a decent dinner, I'm sure you would be able to gain a much better insight into the TP and their 'world' than I can offer in a few sentences.
Old Duffer