Ruby translation, please check and approve :-)
The test cases don't check the case [n > length of the string], but the instructions demand to handle that case:
"If n is greater than the lenght of the string, you should return an array with the only element being the same string."
So currently that part could be left out and you still get to submit your final solution.
Typo in description:
"If n is not a valid size(> 0) (or is absent)" should be <0 (less than 0) rather than greater than 0 as it's describing invalid conditions.
Also a small typo in the next line 'lenght' --> 'length'