I could believe there were unit tests, but not at a high enough level. new_func input:$25,000, output:$25,000. Test passes.

Oh I’m sure there are unit tests for new func and old func that test them separately just fine. The if statement is probably thought of as a temporary switchover kind of thing.

People writing unit tests for internal tools? A lot of companies don't even having tests for production code.

Especially yes. A unit test would have caught this instantly.

It is code that deals with $'s... something you'd really want to test, since it'll cost the company money.

Instead, you've got multiple engineers writing code multiple times (my euphemism for fixing buggy code), which also costs the company money.

I'm just saying people don't do it in practice.