Need help with a test... (still new to the world of testing coroutines) Here's something I've come ...

# coroutines

[Colton Idle]

Need help with a test... (still new to the world of testing coroutines)

Here's something I've come across a bunch

@Test
  fun `assert foo`() = runTest{
    val bar = Bar(coroutineContext)
    bar.sync()
    assertThat(bar.state.sync).isEqualTo("bla")
  }

Bar has sync defined as

fun syncConfig() {
    passedInScope.launch {
      state = "bla"
    }
  }

so. basically. can i do something like this?

@Test
  fun `assert foo`() = runTest{
    val bar = Bar(coroutineContext)
    bar.sync()
    coroutineContext.waitTillAllWorkIsDone() <==== the additional line
    assertThat(bar.state.sync).isEqualTo("bla")
  }

[Francesc]

You have 2 ways to go about this:
• refactor sync to be a suspend function (that'd be my preferred way, having methods that launch and forget lead to issues)
• have the passedInScope provided to whatever class includes syncConfig and in tests pass a test scope, either coroutineContext from runTest, backgroundScope from runTest or some other scope you can control

[Francesc]

you can also return the job from syncConfig and then join that

[Albert Chang]

Adding testScheduler.advanceUntilIdle() after bar.sync() should make it work I believe.

[Albert Chang]

If you would like launch and async calls to be executed automatically, you can also use runTest(UnconfinedTestDispatcher()).

[Colton Idle]

Oooh! advanceUntilIdle worked!

[Colton Idle]

I'm going to try to parse out all of the other suggestions here to see if I'm doing anything "wrong".

[Colton Idle]

• refactor sync to be a suspend function (that'd be my preferred way, having methods that launch and forget lead to issues)

I think I'd like to do that, but my code above is actually a viewModel. So the videwModel has a function that fires a call and then updates some compose snapshot state. so all of the recs I've seen before say that not exposing a suspend fun in ViewModel is a good idea.

[Colton Idle]

• have the passedInScope provided to whatever class includes syncConfig and in tests pass a test scope, either coroutineContext from runTest, backgroundScope from runTest or some other scope you can control

Yeah, that's what I'm doing now. PassedInScope == coroutineContext from val bar = Bar(coroutineContext) sorry that I didn't make that clear enough. 🤦

[Colton Idle]

If you would like launch and async calls to be executed automatically, you can also use runTest(UnconfinedTestDispatcher()).

@Albert Chang hm. I don't think I follow.

[Albert Chang]

https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-test/kotlinx.coroutines.test/run-test.html
https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-test/kotlinx.coroutines.test/-unconfined-test-dispatcher.html
You can read the document.

[Colton Idle]

gracias!

[Colton Idle]

thanks for the push to read those docs. some things definitely seem clearer now. not 100%, but im getting there 🙏