fun main() = runBlocking {
    repeat(50) {
        launch(<http://Dispatchers.IO|Dispatchers.IO>) {
            delay(5000L * it)
            println("Done $it")
        }
    }
}

@Test
fun threads() = runBlockingTest {
    (1..50).map {
        launch(<http://Dispatchers.IO|Dispatchers.IO>) {
            delay(5000L * it)
            println("Done $it")
        }
    }.joinAll()
}

java.lang.IllegalStateException: This job has not completed yet

runBlockingTest

withContext