CoroutineTestRule.kt

@ExperimentalCoroutinesApi
class CoroutineTestRule(
    val testDispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()
) : TestWatcher() {

    val testDispatcherProvider = object : DispatcherProvider {
        override val io: CoroutineDispatcher = testDispatcher
        override val ui: CoroutineDispatcher = testDispatcher
        override val default: CoroutineDispatcher = testDispatcher
        override val unconfined: CoroutineDispatcher = testDispatcher
    }

    override fun starting(description: Description?) {
        super.starting(description)
        Dispatchers.setMain(testDispatcher)
    }

    override fun finished(description: Description?) {
        super.finished(description)
        Dispatchers.resetMain()
        testDispatcher.cleanupTestCoroutines()
    }
}