>Assuming a fully tested codebase, there is an overhead in writing and maintaining unit tests that has to be considered as well, and using a static type system

>Assuming a fully tested codebase, there is an overhead in writing and maintaining unit tests that has to be considered as well, and using a static type system obviates a whole category of them. I've not found this to be true, and tests that do type checking are a waste of time in any language. Bugs that are caught by static type systems are almost always caught by a combination of behavior tests and a sprinkling of sanity/type checks on border code (e.g. a module's publicly facing API). >you'll find out at compile time what you did wrong In a fully tested code base that is regularly tested the distinction between compile time and runtime does not matter a lot. By contrast n code bases in dire need of tests (which is more common than generally assumed), the distinction is absolutely vital.