如何在单元测试中注入协程调度程序 - 使用 Koin

Question

I am injecting my dispatcher, using Koin, into my classes

Extract of one class using Koin

class LogsWorker(
    val context: Context,
    workerParameters: WorkerParameters
) : CoroutineWorker(context, workerParameters), KoinComponent {


    private val ioDispatcher: CoroutineDispatcher by inject()
}

koinModule:

val appModule = module {
    factory { provideIoDispatcher() }
}

private fun provideIoDispatcher(): CoroutineDispatcher = Dispatchers.IO

If I want to unit test my LogsWorker class, I need to inject a coroutineTestDispatcher. How could I do that? I don't find any example anywhere.

Answer 1

You need to override that bean definition in your testing, when you are loading you are starting koin and loading the modules.

You can do that with: factory(override = true) { provideYourTestingDispatcher }

Read more about it here

Although the above could work, I just find it more elegant to use constructor injection instead, for ex:

class LogsWorker(
    val context: Context,
    workerParameters: WorkerParameters,
    private val ioDispatcher: CoroutineDispatcher
) : CoroutineWorker(context, workerParameters)

Then you can just specify the definition for LogsWorker in koin, such as:

factory { (context: Context, workerParameters: WorkerParameters) -> LogsWorker(context, workerParameters, get()) }

And in testing, you can just simply pass in the testing dispatcher. More info about this: https://insert-koin.io/docs/reference/koin-core/injection-parameters#defining-an-injected-parameter

UPDATE: override is deprecated, you could use KoinApplication.allowOverride(true) instead