Hello I m trying to validate my Google findings Is it accura

Question

Hello I m trying to validate my Google findings Is it accurate to say that the best only approach to making this testable is to have a dispatcher provider that masks which `Dispatcher` is provided during testing

streetsofboston · Answer

No If you `launch` it on the CoroutineScope that is or is a child of your runBlocking s or runBlockingTest s CoroutineScope your test won t finish until all you asynchronous code has finished with good result or an exception However if you have delays timeouts etc and you don t want to have long running tests or when you launch async code from different CoroutineScopes then using runBlockingTest with its TestCoroutineDispatcher is of great use since you can fast forward through time

streetsofboston · Answer

Of course the best approach may still be to make the dispatcher injectable providing it Just in case you do in the future add delays timeouts etc

Javier · Answer

Currently with `runBlockingTest` being not multiplatform and so buggy I think there is no way to testing properly without injecting it confused

Javier · Answer

streetsofboston · Answer

For most you can just use runBlocking

Javier · Answer

not same runBlocking doesn t have the test dispatcher

streetsofboston · Answer

But most of the time you don t need that dispatcher just let the runBlocking run its course

Javier · Answer

so you are forced to inject at least the coroutineContext if you are testing things like stateflow

Javier · Answer

yeah but should be great I have no need to inject it in viewmodels for example for testing the stateflow and so on

streetsofboston · Answer

Yup with stateflow you probably use different coroutinescope to launch start them Then a simple runBlocking may not be sufficient

streetsofboston · Answer

But for testing plain suspend funs cold flows etc runBlocking is often enough

Javier · Answer

yeah because stateflow conflates I need the test dispatcher to resume pause

Javier · Answer

and with runBlockingTest it just fail issue I shared above

rook · Answer

There s one detail I omitted on line 3 that may make a difference The line actually reads `customScope launch <http Dispatchers IO|Dispatchers IO> `

rook · Answer

< streetsofboston> If you ll notice I am actually using `runBlockingTest` in my test however the launch block appears to not have time to complete before I try to verify the results

rook · Answer

I was hoping that `runBlockingTest` would actually await completion of the block but it seems that because the scope is custom I won t be able to rely on that

rook · Answer

perhaps the method itself should be suspending instead of restricting the single piece of processing to a different Job

mkrussel · Answer

You could move the verification code outside the `runBlockingTest` so that the launch has finished before you do your asserting Even though most samples show `fun test = runBlocking` you can place the `runBlocking` inside the body of a normal test method