They didn't test against pointy embedded rocks, because there where few of those where the small rovers had been. The main problem was the angle of the front a

They didn't test against pointy embedded rocks, because there where few of those where the small rovers had been. The main problem was the angle of the front and legs: if you drag a rolling suitcase up a curb it's all good, but when you try to push it up, you can generate forces much higher than the weight of the suitecase. Same happened to the rover.