[TimJYoung]

"Static typing is just for internal quality."

Frankly, I don't even know what to do with such a statement. What is your definition of "internal" ?

I just did a very large re-factor of a codebase a few days ago where I changed a lot of event handler (method) types in a codebase of around 200K lines of code (Object Pascal). This means that the method signature of every single event handler could have been wrong in some way if I made a mistake, and it would have introduced a pretty egregious, non-internal bug in every case. How would you test such a massive change without replicating every single thing that a static type system and compiler already do for you ?

[tom_]

This has been my experience too. I've done a bunch of these sorts of changes over the years in C++. It's very straightforward: break code, fix errors, run code, fix remaining bugs (if there are any), commit code.

None of these projects had unit tests, but that's fine - you don't really need them for this sort of modification, just some patience, a tolerance for boredom (that, or the ability to suck it up anyway), and a complete lack of concern about messages such as 'ERROR: 0/1,577 file(s) built. NOTE: Error limit exceeded - only showing the first 99,999'.

[qwer]

Well let me first remind you that you're in a javascript thread. OO Pascal is strict enough that you're not going to get the opportunity to see things work when they get types that they didn't expect because the compiler is unforgiving. So that's going to be hard for you to imagine, but it happens in javascriptland. A function in javascript meant to take a number to output "X hours ago" could very easily get the string "3" and still do exactly what the user expects. That's what I mean by an incorrect type that is internal only, and not a user-facing bug. This is an overly simplified example too. With duck-typing you can often get away with all kinds of not-the-type-that-the-method-expected and live to tell the tale.

I haven't touched OO Pascal in 15 years, so I can't speak to how you would write tests for it, or if there's even a testing framework. I will tell you that I left the if-it-compiles-it-works attitude around that time too though.

[TimJYoung]

Yes, I understand how JS works. My company markets and sells a web development IDE that includes an Object Pascal->JS compiler.

Re: your definition of "internal": I suspected that this was what you meant. I also disagree with this particular version of "correctness". If the developer intended that a particular function accept an integer, then accepting anything else is essentially a bug, and the fact that it works at all is down to pure coincidence.

As for writing tests in OP: you write tests in the same manner that you do with Java, C++, C#, etc.