For example now I'm building a Servant API on Haskell. It's basically a strongly typed API that you don't need to validate with tests. You only need to test the

For example now I'm building a Servant API on Haskell. It's basically a strongly typed API that you don't need to validate with tests. You only need to test the handlers that handle business logic. In other languages with a less sophisticated type systems I would need to build validation functions manually and obviously test them. Hell, an interpreted language might even boot up with functions that have faulty code, ultimately producing runtime errors when invoked. Haskell generally would not (because of the type system). Adding type constraints basically limits the range of possible inputs/outputs, requiring you to write far less tests.