Why would `to_roman(5)` be V, but `to_roman(21)` be an array of 2 and 1, and `to_roman(20)` be an array of "X" and "X"? Wouldn't 21 be equal to XXI? Why would 5 return a roman numeral string, but 20 return an array of roman digits? Reading these conflicting tests, I'm having a hard time understanding what you intended your method to do.