Espresso IdlingResource for RxJava tests

Example @Test

    @After
    public void release() {
        Espresso.unregisterIdlingResources();
    }
    
    @Test
    public void buttonShouldUpdateText() {
        // may put following 3 lines into @BeforeEach annotaded method as well
        rxEspressoScheduleHandler = new RxEspressoScheduleHandler();
        RxJavaPlugins.setScheduleHandler(rxEspressoScheduleHandler);
        Espresso.registerIdlingResources(rxEspressoScheduleHandler.getIdlingResource());
        
        onView(withId(R.id.button)).perform(click());
        // this action happens after delay - for example after network call through RxJava Observable
        onView(withId(R.id.resultView)).check(matches(withText(containsString("Result"))));
    }

RxEspressoScheduleHandler.java

import android.support.test.espresso.IdlingResource;
import android.support.test.espresso.idling.CountingIdlingResource;

import io.reactivex.annotations.NonNull;
import io.reactivex.functions.Function;

public class RxEspressoScheduleHandler implements Function<Runnable, Runnable> {

    private final CountingIdlingResource countingIdlingResource = new CountingIdlingResource("rxJava");

    @Override
    public Runnable apply(@NonNull final Runnable runnable) throws Exception {
        return new Runnable() {
            @Override
            public void run() {
                countingIdlingResource.increment();

                try {
                    runnable.run();
                } finally {
                    countingIdlingResource.decrement();
                }
            }
        };
    }

    public IdlingResource getIdlingResource() {
        return countingIdlingResource;
    }

}