It's just to use monkeypatching and not to provide your own version of upcase. :)

Since you've done that, can you also make it so that the "upcase" method can't be used? Or is the point just to use monkeypatching and not to actually implement an upcasing method?

Ok solved it by adding a new test case that checks if alias was used.

I like the level it's at - if you're not familiar with ruby indexing, it's a good beginner kata without adding restrictions. And the reason I didn't say "array" is because I want new developers to get used to hearing real-world descriptions. Your boss/client won't ask for an "array" of customer names, for instance. I want the developer to figure out the rest, and I use the example tests to ensure they know exactly what's expected of them.