Looks like `withData()` in isolation mode `Instanc...

# kotest

[Lukasz Kalnik]

Looks like withData() in isolation mode InstancePerTest and InstancePerLeaf doesn't support multiple arguments when one of them is random (or otherwise generated, I'm using Instancio) and the others are based on the first one:

val a = Random.nextInt().toString()
val b = "101$a"
val c = "010$a"

withData(a, b, c) { a -> println("withData: $a") }

prints only the first argument (the test doesn't run for b and c):

withData: 1234664241

[Lukasz Kalnik]

Kotest 5.9.1,
isolationMode = InstancePerTest
Test is nested in a FreeSpec

[Lukasz Kalnik]

This minimal reproducer throws `NoSuchElementException`:

class MyTest : StringSpec({
    isolationMode = InstancePerTest

    val a = Random.nextInt().toString()
    val b = "101$a"
    val c = "010$a"

    withData(a, b, c) { t -> println("withData: $t") }
})

[Lukasz Kalnik]

exception.log

exception.log

[Lukasz Kalnik]

When using InstancePerLeaf instead, the test doesn't throw, but only executes the test with the first argument.

[Lukasz Kalnik]

Only with SingleInstance it works as expected.

[Lukasz Kalnik]

Looks like the problem has been caused by the arguments not being stable (I suppose it means that the arguments cannot be resolved after the test is done).
I could work around the problem by assigning explicit names for each of the arguments:

withData(
    mapOf(
        "Random" to Random.nextInt().toString(),
        // ...
    )
) {
    // ...
}

[Lukasz Kalnik]

Would it be possible to give a more clear error in this case?

[sam]

I think it must be because the test names are changing between instances, so I think we could throw an error saying the test couldn't be found when the next spec is instantiated