RxJava 2 overriding IO scheduler in unit test

Question

I\'m trying to test the following RxKotlin/RxJava 2 code:

validate(data)
    .subscribeOn(Schedulers.io())
    .observeO         


        

Answer 1

As an alternative to proposed solutions, this has been working fine for a while in my projects. You can use it in your test classes like this:

@get:Rule
val immediateSchedulersRule = ImmediateSchedulersRule()

And the class looks like this:

class ImmediateSchedulersRule : ExternalResource() {

    val immediateScheduler: Scheduler = object : Scheduler() {

        override fun createWorker() = ExecutorScheduler.ExecutorWorker(Executor { it.run() })

        // This prevents errors when scheduling a delay
        override fun scheduleDirect(run: Runnable, delay: Long, unit: TimeUnit): Disposable {
            return super.scheduleDirect(run, 0, unit)
        }

    }

    override fun before() {
        RxJavaPlugins.setIoSchedulerHandler { immediateScheduler }
        RxJavaPlugins.setComputationSchedulerHandler { immediateScheduler }
        RxJavaPlugins.setNewThreadSchedulerHandler { immediateScheduler }

        RxAndroidPlugins.setInitMainThreadSchedulerHandler { immediateScheduler }
        RxAndroidPlugins.setMainThreadSchedulerHandler { immediateScheduler }
    }

    override fun after() {
        RxJavaPlugins.reset()
    }

}

You can find a way to migrate from TestRule to ExternalResource here and get more info on testing RxJava 2 here.