Provide RandomSource in PropertyContext

For certain tests it might be useful to have access to a deterministic random source. For example when working on (large) lists with expensive computations, where it is too expensive to verify all combinations exhaustively. Or simply when one element or a subset must be selected.

It would be helpful to be able to simply call: val element = theCompleteList.random(random)

Omitting the random argument results in a test that is not repeatable.

Since the properties execute in the context of PropertyContext, it would be possible to proved the randomSource as a public member.

[tbvh]

Sorry to complicate this further. I’ve just created https://github.com/kotest/kotest/issues/3076, suggesting the possibility to run the shrunk case, by skipping over the large iterations.

This new feature requires that the random source is completely controlled by the kotest framework, and no interactions with it are outside the framework. This should be taken into account when solving this issue (https://github.com/kotest/kotest/issues/3046).

Instead of providing the actual random source from the framework, my suggestion is to create a new Random, seeding it it from the frameworks random source, and injecting the new Random into the test context. This way the RandomSource of the framework remains isolated from the Random provided to the test.

[sksamuel]

Instead of providing the actual random source from the framework, my suggestion is to create a new Random, seeding it it from the frameworks random source, and injecting the new Random into the test context. This way the RandomSource of the framework remains isolated from the Random provided to the test.

So in other words, using the provided random source wouldn’t move the framework’s random source on? So we’d create a “seed” random from the seed value, and then use that to generate a random per test, which would be fed into the test for users to use?

Something like

val seedRandom = Random(seed) for (iteration in iterations) { val testRandom = Random(seedRandom.nextLong()) }