Well, that's one code practice opinion. It's valid, if you're going for "functional programming", but if you're not, and trying to go for more efficiency, it may be better to use objects that already exist, rather than spending time and memory duplicating the whole thing. Especially in these little kata tests. IMO they should be about problem solving, not programming best practice.

Never modify function arguments that aren't simple primitive values!

@constablebrew Oh, come on. You aren't just blocking us from using the input, are you? That just means we've got to make a whole copy of the entire thing. Could you not just pass in a copy of the array within the test? That would save a lot of annoyance, I feel.

@constablebrew Oooh. That'll be the problem with mine, then. I'll see if this has fixed my issue.

Thanks for reminding me :)

It looks like you are modifying the input array, which in turn modifies the values in the test fixture. I will need to modify the test fixture to ensure that this is detected.

Edit: All set - you should now get an error message stating that the input array was modified.

Can you post your code here (mark as spoiler)? and I'll take a look.