This was probably just a silly example for a quick explanation. But all it takes is a method that expects an integer Id to receive a string representation of

This was probably just a silly example for a quick explanation. But all it takes is a method that expects an integer Id to receive a string representation of said id because of some obscure path in code that notwithstanding your 100% line coverage the team is so proud of, was never exercised on tests because nobody can have 100% branch coverage