The "threat" of having to add unit tests should force developers to write their classes and components in a way that is easy to reason about. In particular: * p

The "threat" of having to add unit tests should force developers to write their classes and components in a way that is easy to reason about. In particular: * put as much functionality into pure functions * depend less on statically-linked globals * import all significant collaborators across seams that can be mocked. * keep state in a small atom, rather than strewn about If you write code like that, you get many of the benefits of unit tests, whether or not they are actually written. Perhaps it's a good idea to write a test harness (e.g. larger integration tests) for old so that you have a reasonable chance of catching it if it becomes broken, and focus on writing new code in a testable fashion.