If you're intrigued by this approach, or perhaps by a similar approach with typescript, I highly recommend checking out a strictly strong typed language at some point. I've been coding in Elm and a little in Haskell, and I find that the type checking is so thorough and exhaustive that I only need to write very few tests to get strong guarantees. This was a very pleasant change from Rails where you are encouraged to aim for 100% code cov, and as such, would spend well over 40% of my development writing tests.