Unlikely. Maybe if you are using a language with a complete type system (let's face it, you are not), but otherwise you are necessarily going to have to encode all the type information into your tests anyway, so you haven't gained anything on this front. A partial type system cannot replace these tests.
Your other points are the real wins, though.
It's literally impossible to write tests to find all bugs. Most tests don't come remotely close to that, so there's always going to be bugs that static type checks find that tests don't.
There's a great paper that shows that even after tests, Typescript would catch 15% of Javascript bugs: https://earlbarr.com/publications/typestudy.pdf
Also the fact static typing eliminates entire classes of bugs means you need to write far fewer tests. I've seen Python tests that literally fed different types into functions and verified that they accepted them. What a misguided waste of effort!
It is always telling when someone starts getting worked up about something, especially when that something wasn't even said or implied.
> Also the fact static typing eliminates entire classes of bugs means you need to write far fewer tests.
You don't need to write any more tests in the absence of static types. The purpose of testing is not to act as a replacement for static types and if you find yourself writing tests just for the sake of testing types, you know you're doing something horribly wrong. But, you necessarily have to encode type information into the tests in order of them to execute. After all, if that wasn't the case, you wouldn't even be able to catch bugs with a type system. As such, you gain that indirectly.
> I've seen Python tests that literally fed different types into functions and verified that they accepted them. What a misguided waste of effort!
Sure, I've seen developers do all kinds of stupid things too. In fact, give them Typescript and they will just litter the code with `any` everywhere – something I've witnessed far too often. There is no technical solution to bad developers. Was there supposed to be some meaningful takeaway here?
To achieve the same level of quality, yes you absolutely do. This is actually a fairly fundamental fact about static typing. Static typing is a weak form of formal verification, or equivalently formal verification is just really really strong static typing. Clearly you don't need to write as many tests for formally verified code. The same is true (to a lesser extent) for "ordinary" static typing.
> Sure, I've seen developers do all kinds of stupid things too.
It's not stupid if you have a static typing system available! The stupidity was relying on tests to verify types, instead of ... you know, the thing whose whole purpose is to verify types.
And as I said in the other comment, tests won't catch all of the mistakes that static typing will catch anyway.
