I just stumbled on this thread. Personally I don't think that any ordinary test really applies. Shakespeare was a literary genius but no prophet. Many have performed miracles or apparently so, but to me that could be a sign of a good magician who knows how to create illusions. It's certainly not in any worldly attainments because many have created immense empires that have endured for hundreds of years without being a prophet.
To me Ramakrishna's statement is a pointer: "When the flower is ripe, the bees come of their own accord." There is something invisible about a true prophet that attracts those whose hearts are open to receiving the truth. In the Jewish tradition the same point is made in a different way but one that points in the same direction "I traveled to the Maggid not to hear Torah from him, but to see how he ties and unties his shoelaces." In the Sermon on the Mount, another way of expressing it is "For he taught them as one having authority, and not as the scribes."
Since we don't live in the time of Muhammad, Jesus or the Baal Shem Tov, how can we today evaluate whether someone had exalted spiritual status, especially given that we are ordinary people. To me there's no sure way. But if our hearts are satisfied that we've found someone whose life inspires us and whose teachings help us orient our lives in an upward direction we've at least made a good choice.
