Positive vs negative testing. Checking the algorithm is generally positive testing. You still should have negative testing, and in a strong type system language

Positive vs negative testing. Checking the algorithm is generally positive testing. You still should have negative testing, and in a strong type system language the compiler can be leveraged to do much more of that for you. But yes, there's a lull with type checking that makes people believe only negative testing is sufficient, which is as foolish as thinking only positive testing is sufficient.