I once encountered old code where many of the functions had an argument "bool isUnitTest". Counting the number of things that have to be wrong with the workplace in order for this to occur and to be acceptable is left as an exercise for the reader.

Worst codebase I have ever seen. The incumbents had zero interest in paying down technical debt. Unit tests were just another thing that could be used to game metrics and justify budgets.

Metaphorically speaking, the group issued predatory high-interest payday loans to keep the customer paying increasing amounts of interest on a growing amount of technical debt, forever.