Also, the idea behind reminding the user to return an array where length === input.length + 1 was another way of aligning the zero-indexed arrays with the nature of the kata. Basically, the test was trying to make sure the user didn't forget to include the first null/nil of the array.

Sorry. Are we referring to the second describe block in the Sample Test Cases? Just want to make sure it's somewhere!

Your solution should return an array with a length of input.length + 1

This is missing from the Ruby translation and the expected length was not clear.

Much appreciated!

I hear you. The test cases in the example test case might've helped, too! There were ten sample test cases in that section, as well as a describe block explaining: "Your solution should return an array with a length of input.length + 1"!

I'll keep that in mind for next time, though :)