Is there any way to use one arb's result to feed t...

# kotest

[dave08]

Is there any way to use one arb's result to feed the function params for another arb and make a pair out of them (arb1, arb2 cartesian product)?

[sam]

map ?

[dave08]

In map there's no RandomSource

[sam]

hmmm true

[dave08]

And it'll only produce one arb2 per arb1

[sam]

map could return a pair, but yeah no RS

[dave08]

I need a set of Arb2's for each Arb1, and end up with Pair<Arb1, Arb2> as a cartesian product

[sam]

then what are you doing with the pair

[dave08]

using it in checkAll to run the tests

[sam]

so you want to do checkAll(arb1, arb2) { a, b -> }

[dave08]

There's a Context object for setting up the repositories and the useCase, and there's a Request object that needs to be set up based on the Context but in many permutations...

[dave08]

yes

[sam]

checkAll(arb1) { a ->
  checkAll(Arb2(a)) { b ->
  }
}

[dave08]

Oh... I see

[sam]

will that do what you want ?

[dave08]

I guess that would do it... but there's nothing to check in the outer checkAll... 🙃

[sam]

doesn't matter, you're just nesting

[dave08]

Ok, I guess that'll do, thanks!

[sam]

cool

[mitch]

@dave08 you may be interested in Arb<A>.flatMap(fn: (A) -> Arb<B>): Arb<B>

[dave08]

I don't think that has a RandomSource either...

[dave08]

Actually... maybe I wouldn't need one there?

[mitch]

If you need access to rs you can do

arb.flatMap { a -> arbitrary { rs -> ... } }

[mitch]

Under the hood kotest will propagate that from the time data is generated from the arb so it's better than nesting check all

[dave08]

That could be a good idea! I'll give it a try, thanks!

[dave08]

Actually, in my current case it's much simpler than I thought:

val contextWithRequestArb = contextArb.flatMap { context ->
        requestArb(context.currState).map { request ->
                context to request
        }
    }

[dave08]

But sometimes that rs is needed, so it's good to know that trick too!

[mitch]

Awesome!