Hi all :android-wave: , How to fix this coroutines...

# coroutines

[Abhimanyu]

Hi all 👋 ,
How to fix this coroutines unit test?

No value produced in 3s

Details in thread 🧵 .

[Abhimanyu]

Test Code

class UsecaseTest {
    private val testDispatcher = UnconfinedTestDispatcher()
    private val testScope = TestScope(testDispatcher)
    private lateinit var SUT: Usecase

    @Before
    fun setUp() {
        SUT = Usecaseimpl(
            coroutineScope = testScope,
        )
    }

    @Test
    fun refresh() = testScope.runTest {
        turbineScope {
            val receiver = SUT.refreshSignal.testIn(
                scope = testScope,
            )
            SUT.refresh()
            assertEquals(
                Unit,
                receiver.awaitItem(),
            )

            receiver.awaitComplete()
        }
    }
}

SUT code

class UsecaseImpl(
    private val coroutineScope: CoroutineScope,
): Usecase {
    override val refreshSignal: MutableSharedFlow<Unit> = MutableSharedFlow(
        replay = 0,
        extraBufferCapacity = 1,
    )

    override fun refresh() {
        refreshSignal.tryEmit(Unit)
    }
}

[Abhimanyu]

As mentioned in Turbine Docs, I have tried with

receiver.cancel()
receiver.awaitComplete()
receiver.awaitError()

And also by replacing testScope with backgroundScope .

> testIn cannot automatically clean up its coroutine, so it is up to you to ensure that the running flow terminates. Use `runTest`'s backgroundScope, and it will take care of this automatically. Otherwise, make sure to call one of the following methods before the end of your scope:
> • cancel()
> • awaitComplete()
> • awaitError()
> Otherwise, your test will hang.

[Abhimanyu]

Changed to this and it worked.

SUT.refreshSignal.test {
            SUT.refresh()
            assertEquals(
                Unit,
                awaitItem(),
            )
        }

I am not able to make it work with turbineScope .

Can anyone please help share what change is required for turbineScope thank you color?

[Daniel Weidensdörfer]

Have you tried StandardTestDispatcher?

[Daniel Weidensdörfer]

Also I think your setup is a bit over engineered. You can use something like:

fun test() = runTest(YourTestDispatcher()) {
    val tested = YourUseCase(scope = backgroundScope)
    
    tested.flow.test {
        awaitItem()
        ...
    }
}

[Abhimanyu]

I have tried standard dispatcher, I had other issues with that.

[Abhimanyu]

The above code still uses test lambda and not turbine scope lambda.


I have also tried the background scope, but it didn't work.

[Daniel Weidensdörfer]

The .test is the turbine lambda.

[Abhimanyu]

Yes, but not turbine scope lambda.
The one used to test multiple flows.

[Daniel Weidensdörfer]

Ah I didnt see your working example. I havent used turbineScope yet.