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

I suggest you take a different approach and add a layer of abstraction to your schedulers. This guy has a nice article about it.

It would look something like this in Kotlin

interface SchedulerProvider {
    fun ui(): Scheduler
    fun computation(): Scheduler
    fun trampoline(): Scheduler
    fun newThread(): Scheduler
    fun io(): Scheduler 
}

And then you override that with your own implementation of SchedulerProvider:

class AppSchedulerProvider : SchedulerProvider {
    override fun ui(): Scheduler {
        return AndroidSchedulers.mainThread()
    }

    override fun computation(): Scheduler {
        return Schedulers.computation()
    }

    override fun trampoline(): Scheduler {
        return Schedulers.trampoline()
    }

    override fun newThread(): Scheduler {
        return Schedulers.newThread()
    }

    override fun io(): Scheduler {
        return Schedulers.io()
    }
}

And one for testing classes:

class TestSchedulerProvider : SchedulerProvider {
    override fun ui(): Scheduler {
        return Schedulers.trampoline()
    }

    override fun computation(): Scheduler {
        return Schedulers.trampoline()
    }

    override fun trampoline(): Scheduler {
        return Schedulers.trampoline()
    }

    override fun newThread(): Scheduler {
        return Schedulers.trampoline()
    }

    override fun io(): Scheduler {
        return Schedulers.trampoline()
    }
}

Your code would look like this where you call RxJava:

mCompositeDisposable.add(mDataManager.getQuote()
        .subscribeOn(mSchedulerProvider.io())
        .observeOn(mSchedulerProvider.ui())
        .subscribe(Consumer {
...

And you'll just override your implementation of SchedulerProvider based on where you test it. Here's a sample project for reference, I am linking the test file that would use the testable-version of SchedulerProvider: https://github.com/Obaied/DingerQuotes/blob/master/app/src/test/java/com/obaied/dingerquotes/QuotePresenterTest.kt#L31