That is just not true. There’s always the option of refactoring, make the necessary changes and manually test the system. Even though I’m a big fan of automated

That is just not true. There’s always the option of refactoring, make the necessary changes and manually test the system. Even though I’m a big fan of automated testing (not only unit tests), most codebases don’t have complete test coverage, but we still refactor and change the systems.