If you were pair programming, your pair could always create a new failing test with the current implementation.
But I’m not pair programming. And you can’t always create a new failing test because int
is a finite type. There are only about 4 billion cases to handle.
Which might take a while to type up manually, but that’s why we have meta-programming: Code that generates code. (In C++ you could even use templates, but you might run into compiler recursion limits.)
More to the point, the risk with TDD is that all development is driven by failing test cases, so a naive approach will end up “overfitting”, producing exactly the code required to make a particular set of tests pass and nothing more. “It can’t pass all test cases”? It doesn’t have to. For TDD, it only needs to pass the tests that have actually been written. You can’t test all combinations of all inputs.
(Also, if you changed this function to use modulus, it would handle more cases than before, which is a change in behavior. You’re not supposed to do that when refactoring; refactoring should preserve semantics.)
@tetris11 @Aedis More like:
isEven() { case "$1" in *[02468]) return 0;; *) return 1;; esac;}
(If all the line breaks are gone from this code snippet, blame Lemmy. It looks fine here.)