I am testing viewModel using the new coroutines testing framework and Mockk library. It seems that t...

# coroutines

[Marek Kubiczek]

I am testing viewModel using the new coroutines testing framework and Mockk library. It seems that the exceptions from child coroutines are swallowed though.
It looks more or less like this example:

@Before
fun setUp() {
  Dispatchers.setMain(UnconfinedTestDispatcher())
}

@Test
fun `Some exemplary test`() = runTest {
    val dependency1 = mockk<Dependency1>()
    val viewModel = TestedViewModel(dependency1)
    viewModel.testedMethod()
    coVerify(exactly = 1) { dependency1.methodToBeCaled() }
}

The ViewModel itself is calling that method in viewModelScope

fun testedMethod() {
  viewModelScope.launch {
    methodToBeCalled()
  }
}

However I forgot to mock the called method. I am seeing in log

Exception in thread "Test worker @coroutine#7" io.mockk.MockKException: no answer found for: Dependency1(#1).methodToBeCalled(continuation {})

But the test passes.

Is it known issue?

[ephemient]

https://github.com/Kotlin/kotlinx.coroutines/issues/3298
coroutines in viewModelScope under setMain don't run immediately as expected :(

[Marek Kubiczek]

And according to runTest doc

Unhandled exceptions will be thrown at the end of the test. If the uncaught exceptions happen after the test finishes, the error is propagated in a platform-specific manner. If the test coroutine completes with an exception, the unhandled exceptions are suppressed by it.

that’s the case here right?

[ephemient]

I believe so. you could add more logging to check that is the order of operations