For instance, with history, whether or not you believe that John F. Kennedy was assassinated doesn't change the fact that he either was (for which the evidence is overwhelming) or wasn't (if, by some amazing chance, the YouTube conspiracy videos are true).
But you bring up a point worth expanding upon. You mention testing. With history, and many other subjects, we can't directly evaluate things in the way that we test things with science. That is to say, we can't go back in time and take a snapshot of a historical moment and say, "There! That did actually happen!"
Some people have (mistakenly, in my mind) concluded that because we can't test a philosophical conjecture the way we can test a scientific conjecture, it's therefore not worth spending time pursuing philosophical truth. I think they just get so hung up on the scientific method that they try to apply it to things that are totally outside its domain.