Thank you - I've now added validation to not allow numbers as Strings.

Hey - being kind to someone who's trying for the first time is also not a novel concept. I appreciate that I'm not doing it in the ideal way - I am still learning. Genuine thanks for your feedback but please try to remember what it was like when you were starting this journey.

Thank you again.

Apologies! I had cleaned up everything except the initial solution. (rookie mistake)
It should be more obvious now.

Added tests as suggested. Thank you.

Thanks for the feedback. I've cleaned up the description, so hopefully it's more obvious. :)

Thank you for your feedback. I'll try to correct the issues before republishing it.