[chuzz]

That's why Typescript/Python optional typing hit the best balance for me. Coding in duck-typed language is generally fine when your test suite is as fast and frequent as a type checker. That also explains why TDD is more popular in say Ruby or Python vs. Java. Speaking of Java, the problem with types is when you try to reify every single problem you encounter in your codebase. By the way, python has structured types since 3.8, and I hope they get more popular in Python code: https://docs.python.org/3/library/typing.html#typing.Protoco...

[youerbt]

> That also explains why TDD is more popular in say Ruby or Python vs. Java.

I'd say that TDD being more popular in untyped languages speaks against TDD, as it hints that maybe some of its benefits are covered already by a type system.

[bluGill]

You did clarify latter a bit, but this cannot stand unchallenged. TDD and tests solve different problems from types and so are valuable for that. Tests assert that no matter what you change this one fact remains true. Types assert that you are using the right things in your code.

I don't think it is lack of types at fault for untyped languages liking TDD (though I miss types a lot). I think it is there is no way to find out if functions exist until runtime (most allow self modifying code of some form so a static analysis can't verify without solving the halting problem). Though once you know a function exists the next step of verifying the function (or an overload in some languages) exists does need types.

[dlahoda]

types are just autoverified logic. tdd just tests logic which cannot be typed in given type system. in lean4 one can type a lot(dependant types to test integration shapes and proofs are proptests).

[marcosdumay]

It's blatantly obvious that some of the benefits of extensive testing are covered by a type system. Even by a mostly useless one like Java's.

If you look at any well tested program in a dynamic language, almost all the tests check the same properties that a type system would also check by default. If you remove those, usually only a few remain that test non-trivial properties.

EDIT: And I just love that in the time I took to write this, somebody wrote a comment about how it isn't so. No, it is still blatantly obvious.

[hitchstory]

Id say if you think tests and types are doing the same thing in the same way you are badly abusing at least one of them.

One attacks the problem of bugs from the bottom up and the other from the top down. They both have diminishing returns on investment the closer they get to overlapping on covering the same types of bug.

The haskell bros who think tests dont do anything useful because "a good type system covers all bugs" themselves havent really delivered anything useful.

[sevensor]

The article makes one of my favorite points about types: types aren’t there to constrain you; what they constrain is the complexity of the program.