[kortilla]

Perhaps in some world where you never modify a type (e.g. concatenate/truncate strings, multiply numbers, etc). Type systems check types, they don’t help verify correctness of the logic performed on the types.

For an example, dig into some crypto libraries. They operate on bytes all over the place performing XORs, etc. A type system isn’t really gonna help you ensure you got the correct number of AES rounds and stitched the blocks in the right order.

IMO the only systems where this “type system eliminates most tests” philosophy seriously works are the ones that don’t do anything other than pass data between components without doing anything beyond calling some serialization methods.

[antris]

> IMO the only systems where this “type system eliminates most tests” philosophy seriously works are the ones that don’t do anything other than pass data between components without doing anything beyond calling some serialization methods.

Which is what 90% of programmers on this website are essentially doing. And for the remaining 10% there is likely a better suited, different programming language or type system available. Even if there isn't unit tests would still be very niche and the general case would be that by default you shouldn't be unit testing.