Needed for Tests with RxJava Schedulers

ImmediateSchedulersRule.java

import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

import io.reactivex.plugins.RxJavaPlugins;
import io.reactivex.schedulers.Schedulers;

public class ImmediateSchedulersRule implements TestRule {

   @Override
   public Statement apply(final Statement base, Description description) {
       return new Statement() {
           @Override
           public void evaluate() throws Throwable {
               RxJavaPlugins.setIoSchedulerHandler(scheduler ->
                                                Schedulers.trampoline());
               RxJavaPlugins.setComputationSchedulerHandler(scheduler -> 
                                                Schedulers.trampoline());
               RxJavaPlugins.setNewThreadSchedulerHandler(scheduler -> 
                                                Schedulers.trampoline());

               try {
                   base.evaluate();
               } finally {
                   RxJavaPlugins.reset();
               }
           }
       };
   }
}