I've dabbled with rust, but did quite a bit of stuff in haskell. A lot of unit testing is verifying failure modes. What happens if they pass in null? What happ

I've dabbled with rust, but did quite a bit of stuff in haskell. A lot of unit testing is verifying failure modes. What happens if they pass in null? What happens if they ask for a value i don't know about? stuff like that. Haskell (and rust) give you a lot more control over what a function is willing to accept at compile time. You could spend your time writing a test to ensure null is handled gracefully. With rust, you have a bit more power, and you can simply ensure the function can't be called with null. It's more general than just null checking, but that's the flavor of what happens.