I don't think `Math.floor() * expected.fileExtensions.length` achieves the goal of generating a random index into the array. I already said that we don't want any randomness in testing, but, for the sake of posterity, I think `Math.floor(Math.random() * expected.fileExtensions.length)` will do what you originally wanted. Note that this will try to access index 0 of an empty array, so that case may need to be isolated.