Is this supposed to be a numeric argument then? Your tests use `'30N'` and `'38S'` but then `'32'` is used in the `EuroPP` constructor... It'd look a lot less confusing if you used just the number consistently and documented it a bit more clearly. My understanding is that the hemisphere is now indicated by a Boolean keyword so it is not required in the zone, and therefore these do not need to be strings?