I think there's a sharp rule of diminishing returns the stronger you make type systems. Type safety comes at a cost and that cost has to come with an associated payoff.
This is why ultra strong type systems end up being little more than academic toys - the payoff when you dial type safety up to an extreme doesn't match the associated cost.
Types and tests should meet somewhere in the middle because the same law of diminishing returns affects tests in reverse. They tend to be good at what the other is bad at and if you rely too heavily on one at the expense of the other they will start fraying around the edges.
This is why ultra strong type systems end up being little more than academic toys - the payoff when you dial type safety up to an extreme doesn't match the associated cost.
Types and tests should meet somewhere in the middle because the same law of diminishing returns affects tests in reverse. They tend to be good at what the other is bad at and if you rely too heavily on one at the expense of the other they will start fraying around the edges.