fails:String#unpack with format 'C' calls #to_str to coerce the directives string
fails:String#unpack with format 'C' adds nil for each element requested beyond the end of the String
fails:String#unpack with format 'c' calls #to_str to coerce the directives string
fails:String#unpack with format 'c' adds nil for each element requested beyond the end of the String
