Kotlin JUnit rules

KotlinRules.kt

import org.junit.rules.TestRule
import org.junit.runner.Description
import org.junit.runners.model.Statement

private class Rule(private val before: () -> Unit, private val after: () -> Unit) : TestRule {
    override fun apply(base: Statement, description: Description?) =
            object : Statement() {
                override fun evaluate() {
                    try {
                        before()
                        base.evaluate()
                    } finally {
                        after()
                    }
                }
            }
}

interface After {
    infix fun after(doThis: () -> Unit): TestRule
}

private class Before(private val doThat: () -> Unit) : After {
    override infix fun after(doThis: () -> Unit) = Rule(doThat, doThis)
}

fun before(doThis: () -> Unit): After = Before(doThis)

Usage.md

Usage

@get:Rule
val myRule =
    before {
       X()
    } after {
       Y()
    }

Rx rules

fun ioSchedulerTrampoline() = Schedulers.trampoline().useForIo()

fun Scheduler.useForIo() =
        before {
            RxJavaPlugins.setIoSchedulerHandler { this }
        } after {
            RxJavaPlugins.reset()
        }

@get:Rule
val ioSchedulerTrampoline = ioSchedulerTrampoline()

val testScheduler = TestScheduler()

@get:Rule
val ioScheduler = testScheduler.useForIo()