Thanks for your help....... I didn't know anything about Guest User until I had the chat with Apple.
The original error says "An error occurred when backing up this user's Home folder." What backup is that?
Good question......... I have no idea.
if you have iCloud Backup turned on, it probably tries to back up all users, try turning that off temporarily, and then back on after the Test User account is successfully deleted.
I don't really use iCloud, I did however go into System Preferences > iCloud > iCloud Drive Options. Nothing there shows anything about a User. The box is checked for iCloud in which I unchecked and made a copy. Went back under "Users and Groups Prefrences" and went through the process again to delete "Test User" and ended up with the same popup as before "An error occurred when backing up this user's Home folder."
I.M.O., Apple chat should have instructed me how to remove this.......... Thanks again for your help I sincerely appreciate it. Ray