It is a bit extreme to assume tests are the pinnacle of high-quality software, or the sole reason that your project will succeed. Tests are one of many pieces required to have a high-quality system and are not more important than any of the other pieces.
I'm (and the company I work at) a big advocate for type systems and leveraging them to have sane and logical representations of our systems' states. This reduces the need for tests DRAMATICALLY. i.e. Rather than writing a unit test to ensure some non-sensical state pops up. Why not leverage the typesystem to make non-sensical states impossible to represent in the first place?
Check out this post discussing type systems to help avoid mistakes.
Also, there's a good talk from the Elm community about making non-sensical states impossible to represent (link) - again reducing the need for tests.
Yes, I absolutely agree that type systems helps a lot. I would actually not use a dynamically typed language for any critical system. This actually increases the number of tests and his right to an unbearable amount. I did that once...
Actually, I’m also a big fan of state machines. I am an electrical engineer and I was working for years in embedded projects. I actually replaced a lot of code that had bugs frequently to use proper state machines. However, because we use Java I needed to write at least a couple of tests.
So, there is always some nice language that may improves your code or reduces the number of tests you need to write. I actually like Haskell and Erlang for different reasons very much. But I would not use them for professional projects because I would not be able to hire any developers in my team. For my professional life I need to stick with Java which is at least not dynamically typed although there is a lot to be improved...
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