Test Rxjava

gistfile1.txt

@BeforeClass
public static void setUpRxSchedulers() {
    Scheduler immediate = new Scheduler() {
        @Override
        public Disposable scheduleDirect(@NonNull Runnable run, long delay, @NonNull TimeUnit unit) {
            // this prevents StackOverflowErrors when scheduling with a delay
            return super.scheduleDirect(run, 0, unit);
        }

        @Override
        public Worker createWorker() {
            return new ExecutorScheduler.ExecutorWorker(Runnable::run);
        }
    };

    RxJavaPlugins.setInitIoSchedulerHandler(scheduler -> immediate);
    RxJavaPlugins.setInitComputationSchedulerHandler(scheduler -> immediate);
    RxJavaPlugins.setInitNewThreadSchedulerHandler(scheduler -> immediate);
    RxJavaPlugins.setInitSingleSchedulerHandler(scheduler -> immediate);
    RxAndroidPlugins.setInitMainThreadSchedulerHandler(scheduler -> immediate);
}

https://stackoverflow.com/questions/43356314/android-rxjava-2-junit-test-getmainlooper-in-android-os-looper-not-mocked-runt