I don't think that's a fair comparison. Testing GUI code has always been a lot trickier than testing backend code, and iOS apps tend to be GUI-oriented while Ruby projects tend to be backend-oriented.
That's not to say that the iOS testing tools are great, but I've never had a particularly pleasant time testing GUI code on any platform.
True, Ruby doesn't usually get used for GUIs. But take a look at the Javascript and browser testing tools that are available. Is there anything like Sauce Labs for iOS?
That's not to say that the iOS testing tools are great, but I've never had a particularly pleasant time testing GUI code on any platform.