Hacker News Reader

Comment by mason55 | Hacker News Reader

The two are completely unrelated. When I was writing vanilla JS it felt like half my tests were just focused on ensuring that everything remained the type it was supposed to be. Not in a static type sense but in a duck type sense at least - does this object still have field X? Can I still call function Y on this object? Is this variable still defined?

All those kinds of tests can be eliminated with static typing. It's true that a lot of those types of errors would get picked up in functional tests, but at least from my perspective it's not great practice to rely on a functional test to catch that kind of change. If your functional test changes it's easy to lose coverage of your basic unit tests that were only happening implicitly.

View on HN

Funny how you say the two are completely unrelated and then go on to show how they are related with your personal experience.

While you're technically correct, this misses the value of static type checking vs type checking in tests. Tests must be written manually, must check every code path and must be updated whenever the underlying implementation changes, in order to achieve the results of static type checking. But types are declarative and will be checked automatically for every code path called.

1. If you dob't have tests covering code, sure type checks are better than nothing. but if you do, why do you also need type checks?

2. If the tests must be updated whenever the underlying implementation changes it might be testing too much- it's better to test behaviour, not implementation.

I was addressing the above comments about tests that specifically check types. My position is that declarative types and a type checker are better because each code path is checked automatically without writing additional tests, and because the type checker automatically adapts without changing or writing new tests when the implementation changes. Testing behavior is another thing entirely.

I'm not missing the value we just have a different idea of what that value is, but anyway, this is a different, more specific topic than the one I originally brought up and one that I don't feel like engaging in.

I think it exactly addresses your original topic, but you're in no way obligated to engage it further. Have a nice day!

Reply on news.ycombinator.com