Exactly. IMO, there was nothing at all wrong with that cave. Yoda set it all up in Luke's head by telling him it was a domain of evil. But he also tried to hint that it might not be true by telling him that the only thing in there was what he took with him and that he would not need his weapons. Luke went in there expecting the worse, found it, and attacked it. That was his failure. But Yoda probably could have had the same results with this test of Luke if he'd told him that the local 7-11 was a domain of evil.