text: package org.mifos.mobile.util;
  
  import org.junit.rules.TestRule;
  import org.junit.runner.Description;
  import org.junit.runners.model.Statement;
  
  import java.util.concurrent.Callable;
  
  import io.reactivex.Scheduler;
  import io.reactivex.android.plugins.RxAndroidPlugins;
  import io.reactivex.functions.Function;
  import io.reactivex.plugins.RxJavaPlugins;
  import io.reactivex.schedulers.Schedulers;
  
  
  /**
   * This rule registers SchedulerHooks for RxJava and RxAndroid to ensure that subscriptions
   * always subscribeOn and observeOn Schedulers.immediate().
   * Warning, this rule will reset RxAndroidPlugins and RxJavaPlugins before and after each test so
   * if the application code uses RxJava plugins this may affect the behaviour of the testing method.
   */
  public class RxSchedulersOverrideRule implements TestRule {
  
      private final Scheduler SCHEDULER_INSTANCE = Schedulers.trampoline();
  
      private Function<Scheduler, Scheduler> schedulerFunction =
                                                          new Function<Scheduler, Scheduler>() {
          @Override
          public Scheduler apply(Scheduler scheduler) throws Exception {
              return SCHEDULER_INSTANCE;
          }
      };
  
      private Function<Callable<Scheduler>, Scheduler> schedulerFunctionLazy =
                                                  new Function<Callable<Scheduler>, Scheduler>() {
          @Override
          public Scheduler apply(Callable<Scheduler> schedulerCallable) throws Exception {
              return SCHEDULER_INSTANCE;
          }
      };
  
      @Override
      public Statement apply(final Statement base, Description description) {
          return new Statement() {
              @Override
              public void evaluate() throws Throwable {
                  RxAndroidPlugins.reset();
                  RxAndroidPlugins.setInitMainThreadSchedulerHandler(schedulerFunctionLazy);
  
                  RxJavaPlugins.reset();
                  RxJavaPlugins.setIoSchedulerHandler(schedulerFunction);
                  RxJavaPlugins.setNewThreadSchedulerHandler(schedulerFunction);
                  RxJavaPlugins.setComputationSchedulerHandler(schedulerFunction);
  
                  base.evaluate();
  
                  RxAndroidPlugins.reset();
                  RxJavaPlugins.reset();
              }
          };
      }
  }
  