Kotest: compatibility with JUnit TestRule ?

[r3mi]

Is it possible to provide compatibility with JUnit TestRule ?
Several frameworks provide test utilities as TestRules, to be used with @Rule or @ClassRule (exemple : DropWizard's ResourceTestRule or DropwizardClientRule).
Unless there is a way to import or bridge with these TestRules, fully switching to kotlintest is not convenient.

Thanks for the nice work,

[helmbold]

Since TestRules are almost a thing of the past (discontinued with JUnit 5), I think it is not worth the effort. I'm not in the implementation details of JUnit rules but they look a bit hacky and the approach is somehow diametrical opposed to KotlinTest.

However the situation is not satisfying under certain conditions and I would be happy if someone would come up with an adapter that wouldn't affect the rest of KotlinTest.

[r3mi]

thanks for the answser.
Not sure myself how to build such an adapter, emulating the necessary org.junit.runners.model.Statement and org.junit.runner.Description seems a bit complicated.

[sschuberth]

What's the recommended way to do something like the TemporaryFolder rule in kotlintest then? Do we need to manually implement this via interceptTestCase?

[pakoito]

I have a legitimate use case for supporting @Rule. The Android framework and its helper libraries rely on it for test behavior.

One example is the just released architecture-components: https://github.com/googlesamples/android-architecture-components/blob/master/GithubBrowserSample/app/src/test/java/com/android/example/github/ui/user/UserViewModelTest.java#L55

Without that rule it's impossible to unitest that library, as it tries to find a Thread that doesn't exist outside Android environments, and fails with NPE.

[helmbold]

JUnit rules are on their way out with the appearance of JUnit 5, I think. But maybe we could find another solution.

[pakoito]

I ended up doing the Rule code manually, as seen here: https://github.com/kategory/kategory/blob/e5813ebcb17a124ba6841718f8f2275f7ca99cb5/kategory-effects-android-architecture-components/src/test/kotlin/kategory/effects/data/LiveDataTest.kt#L20

[helmbold]

Maybe you want to have a look at KotlinTest interceptors.