Kotlin and kotest with arbitrary values: what am I doing wrong?

Question

I've gone through the kotest documentation and am trying to incorporate some property based testing into my code. From the documentation, my impression was that if you use a forAll<T>, if kotest has a built-in Arb<T>, it would generate arbitrary values for T and then run the given tests on them.

So then, why does this example which should clearly fail claim to pass for me?

class PassesExample: ShouldSpec({
    should("I should fail") {
        forAll<Int> { a ->
            abs(a) shouldBe -1
        }
    }
})

The output is as follows:

> Task :wrapper
BUILD SUCCESSFUL in 98ms
1 actionable task: 1 executed
> Task :compileKotlin UP-TO-DATE
> Task :compileJava NO-SOURCE
> Task :processResources NO-SOURCE
> Task :classes UP-TO-DATE
> Task :compileTestKotlin UP-TO-DATE
> Task :compileTestJava NO-SOURCE
> Task :processTestResources NO-SOURCE
> Task :testClasses UP-TO-DATE
> Task :test
BUILD SUCCESSFUL in 1s
3 actionable tasks: 1 executed, 2 up-to-date
9:42:38 PM: Execution finished ':test --tests "abstractalgebra.PassesExample"'.

(Ignore the abstractalgebra... I'm trying to play around with some finite fields and just threw this in the same file as my test file.)

If I don't use the forAll<Int> and give it an obvious concrete fail case, everything works as expected, for example:

class PassesExample: ShouldSpec({
    should("I should fail") {
        abs(2) shouldBe -1
    }
})

and I get:

expected:<-1> but was:<2>
Expected :-1
Actual   :2

What am I doing wrong? It is obvious that no tests are executed at all, or this would not work.

Answer 1

Never mind: I found out the issue. I was importing the wrong forAll:

import io.kotest.data.forAll

when I should have been importing:

import io.kotest.property.forAll