No Witnesses

There is no fusion going on in brown or white dwarfs. They emit stored thermal energy left over from the fusion reactions earlier in the stars life.I really doubt that you will get something like our Sun from friction. Without fusion you will get something like Jupiter or Saturn. Once a star reaches a certain mass then fusion is unavoidable.

Your question is a bit confusing. I will assume that you meant to say "without the use of fusion".From my understanding, it is impossible for hydrogen to NOT fuse at the center of the Sun given the temperatures and pressures. There is also the fact that we observe neutrinos escaping the Sun which strongly evidences fusion reactions.To bring this back on topic, we don't have to directly witness the fusion reactions in the middle of the Sun to know that they are happening. We can use observations to infer that fusion reactions are occuring.