You will never find me in my dynamic backyard writing such tests neither - I will write normal tests and they still expose type errors. And, if you do not writ

You will never find me in my dynamic backyard writing such tests neither - I will write normal tests and they still expose type errors. And, if you do not write tests, there is a bunch of other problems that will surface, which will not be caught by the compiler itself. What I'm saying is static types give you feedback loop: write code -> make the project compile -> fix bugs while the dynamic ones give you: write code -> fix bugs (including type ones). Obviously, YMMV. For me it works. And to be honest, from my experience nothing is more brittle than a type hierarchy designed early in project lifetime and then fixed repeatedly until it "works", but again - to each their own.