4 ms·

While I am a big fan of property based testing, it’s hardly able to “test everything”. It’s great for testing pure functions, but as soon as things have side ef

While I am a big fan of property based testing, it’s hardly able to “test everything”. It’s great for testing pure functions, but as soon as things have side effects, property based testing becomes very cumbersome. Unfortunately, this is precisely where a large amount of bugs originate from. And I say all this as someone who has pursued this very idea of property testing side effects for years and in the end had to admit failure. It just is too much work get right (eg uuids being generated not unique, to name just one example), and your test runs become incredibly slow, which is a killer in many REPL-driven workflows.

PopeDotNinja 6y ago
I have a (probably horrible) joke reply to the question "what is a monad?" I say "that's where you put the real programming." I have also never done any serious with Haskell, so don't make the mistake of taking me seriously on this :)
- gindely 6y ago
  however true the statement may be, it's not therefore an abandonment of pure functional programming. You don't have to program in `IO` or `MonadIO m => m`. Expressing your state in terms of pure functions of input events, as can be done with an FRP like Reflex, means you can test all your logic purely. You can be confident that you'll only request to launch the nukes when the nukes need to be launched. Then you have to make yourself confident that, when the system asks the nukes to launch, it sends the right signal. But that's mockable by running the system attached to device that reads the signal and reports its correctness. And making sure the nukes take off, aim correctly, and land on their target is not my department (says Werner von Braun).
Jtsummers 6y ago
If you can't capture the side effects to determine if they're correct, you can't test it period. Property based testing, unit testing, or integration testing, doesn't matter.

PopeDotNinja 6y ago

I have a (probably horrible) joke reply to the question "what is a monad?" I say "that's where you put the real programming." I have also never done any serious with Haskell, so don't make the mistake of taking me seriously on this :)

gindely 6y ago
however true the statement may be, it's not therefore an abandonment of pure functional programming. You don't have to program in `IO` or `MonadIO m => m`. Expressing your state in terms of pure functions of input events, as can be done with an FRP like Reflex, means you can test all your logic purely. You can be confident that you'll only request to launch the nukes when the nukes need to be launched. Then you have to make yourself confident that, when the system asks the nukes to launch, it sends the right signal. But that's mockable by running the system attached to device that reads the signal and reports its correctness. And making sure the nukes take off, aim correctly, and land on their target is not my department (says Werner von Braun).

Jtsummers 6y ago

If you can't capture the side effects to determine if they're correct, you can't test it period. Property based testing, unit testing, or integration testing, doesn't matter.