Hi, is is possible with kotest to derive generator...

# kotest

[Stefan]

Hi, is is possible with kotest to derive generators from data classes like with scalacheck-shapeless ?

[sam]

Yes there is bind.

[sam]

I think this is what you want https://github.com/kotest/kotest/blob/master/kotest-property/src/jvmMain/kotlin/io/kotest/property/arbitrary/jvmbind.kt

[Stefan]

yes, thank you! Does it work for nested structures as well?

internal class SomeTest : FreeSpec() {
  
    data class Inner(val t: String)
    data class Outer(val i: Inner)
    init {
      "String size" {
        checkAll<String, Outer>(Arb.string(), Arb.bind<Outer>()) { a, b ->
          a.length shouldBe b.i.t.length
        }
      }
    }
}

[sam]

I don't think so, I'd have to check the code

[sam]

Actually looks like it would https://github.com/kotest/kotest/blob/e9c046b2ffd7f60ced7a6aea0b0014cd6f484b7c/kot[…]rc/commonMain/kotlin/io/kotest/property/arbitrary/reflection.kt

[Stefan]

still "Cannot infer generator for class Some$Outer; specify generators explicitly"

[Stefan]

"String size" {
      checkAll<String, Outer>(Arb.string(), Arb.default()) { a, b ->
        a.length shouldBe b.i.t.length
      }
    }

[sam]

You would need to pass in an arb manually, try this

"String size" {
      checkAll<String, Outer>(Arb.string(), Arb.bind<Outer>()) { a, b ->
        a.length shouldBe b.i.t.length
      }
    }

[sam]

I think we should make it work without needing to specify anything, by defaulting to bind

[sam]

https://github.com/kotest/kotest/issues/2355

[sam]

PR here https://github.com/kotest/kotest/pull/2356