I'm trying to make tests for rendezvous channels t...

# coroutines

[Maciek]

I'm trying to make tests for rendezvous channels that sends data between two separate coroutines but can't find a proper way to do it. Below is the setup I'm trying to test but this code doesn't work, assert is not executed because coroutine suspends on receive and test finishes

Untitled.kt

[Maciek]

I've tried getting job out of first coroutine launch and waiting for it in runBlocking but that resulted in blocking the test indefinitely

[Dominaezzz]

@Test
fun `test channels`() = runBlocking {
	val channel = Channel<Int>()
	launch {
		assert(channel.receive() == 1)
	}
	launch {
		delay(1)
		channel.offer(0)
	}
}

[Maciek]

Thanks for the reply @Dominaezzz, your test works but that's the problem that I needed those separate scopes, different MainScope objects. This is just sample code to simulate architecture that I'm testing. I guess in order to make it testable I have to design code that scope can be injected and replaced in tests

[Dominaezzz]

Ah. and this doesn't work.

@Test
fun `test channels`() {
	val channel = Channel<Int>()
	val job1 = MainScope().launch {
		assert(channel.receive() == 1)
	}
	val job2 = MainScope().launch {
		delay(1)
		channel.offer(0)
	}
    runBlocking { job1.join(); job2.join() }
}

[Maciek]

yup, it hangs forever. Thanks for the idea of using test scope from runBlocking, I've changed the architecture to inject it in the objects constructors and everything works.
But I wonder if this case with separate scopes is testable at all

[Dominaezzz]

I just realised that Dispatchers.Main might not be available in tests. Although I'm not sure if it matters.

[Maciek]

I'm using in the test setup

Dispatchers.setMain(TestCoroutineDispatcher())

so that shouldn't be a problem