Is this expected? This test fails:

@Test
fun test() = runBlocking {
    assertTrue(actor<Unit> { for (it in this) {  } }.offer(Unit))
}

But this test passes:

@Test
fun test() = runBlocking {
    val actor = GlobalScope.actor<Unit> { for (it in this) {  } }
    delay(100)
    assertTrue(actor.offer(Unit))
}

It’s like the actor’s queue needs some time to be set up. It’s not ready right away after creation.

It is expected. It is not about setting up queue. This is not how or why you’d use offer.

The first test fails because your test coroutine never gives the actor coroutine a chance to run. Your second test does this by calling

delay

, but I think you should get the same result if you just used

yield

.

offer

will only succeed if there is a coroutine that is currently suspended waiting for something from the channel. Since the actor never has a chance to run, it never receives from its channel, so the offer fails.