Coroutines setup with org.jetbrains.kotlinx:kotlinx-coroutines-test

MyUnitTest.kt

class MyUnitTest {
    @get:Rule
    val coroutineRule = TestCoroutineRule()
  
    @Test
    fun `my test executed on TestCoroutineDispatcher`() = coroutineRule.runBlockingTest {
        assertEquals(42, answer())
    }
}

suspend fun answer(): Int {
    delay(TimeUnit.DAYS.toMillis(Long.MAX_VALUE))
    return 42
}

TestCoroutineRule.kt

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.test.*
import org.junit.rules.TestRule
import org.junit.runner.Description
import org.junit.runners.model.Statement

@ExperimentalCoroutinesApi
class TestCoroutineRule : TestRule {
    private val testCoroutineDispatcher = TestCoroutineDispatcher()
    val testCoroutineScope = TestCoroutineScope(testCoroutineDispatcher)

    override fun apply(base: Statement, description: Description) = object : Statement() {
        @Throws(Throwable::class)
        override fun evaluate() {
            Dispatchers.setMain(testCoroutineDispatcher)

            base.evaluate()

            Dispatchers.resetMain()
            testCoroutineScope.cleanupTestCoroutines()
        }
    }

    fun runBlockingTest(block: suspend TestCoroutineScope.() -> Unit) =
        testCoroutineScope.runBlockingTest { block() }
}