Has natural selection really been tested and verified?

This is an interesting thought that I hadn't seen before. Of course, evolution can go on with out any RM but (a big but) for how long in what way?NS is selecting out specific patterns. Eventually you'd end up with a very, very restricted gene pool if no new variation is being added. All this would do is hasten the time when the final selection is made and the species goes extinct. Which is perfectly good evolution too.