code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.rxjava3.schedulers;
  
  import static org.junit.Assert.assertTrue;
  
  import java.util.*;
  import java.util.concurrent.TimeUnit;
  
  import org.junit.Test;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  
  public class SchedulerWorkerTest extends RxJavaTest {
  
      static final class CustomDriftScheduler extends Scheduler {
          public volatile long drift;
          @NonNull
          @Override
          public Worker createWorker() {
              final Worker w = Schedulers.computation().createWorker();
              return new Worker() {
  
                  @Override
                  public void dispose() {
                      w.dispose();
                  }
  
                  @Override
                  public boolean isDisposed() {
                      return w.isDisposed();
                  }
  
                  @NonNull
                  @Override
                  public Disposable schedule(@NonNull Runnable action) {
                      return w.schedule(action);
                  }
  
                  @NonNull
                  @Override
                  public Disposable schedule(@NonNull Runnable action, long delayTime, @NonNull TimeUnit unit) {
                      return w.schedule(action, delayTime, unit);
                  }
  
                  @Override
                  public long now(TimeUnit unit) {
                      return super.now(unit) + unit.convert(drift, TimeUnit.NANOSECONDS);
                  }
              };
          }
  
          @Override
          public long now(@NonNull TimeUnit unit) {
              return super.now(unit) + unit.convert(drift, TimeUnit.NANOSECONDS);
          }
      }
  
      @Test
      public void currentTimeDriftBackwards() throws Exception {
          CustomDriftScheduler s = new CustomDriftScheduler();
  
          Scheduler.Worker w = s.createWorker();
  
          try {
              final List<Long> times = new ArrayList<>();
  
              Disposable d = w.schedulePeriodically(new Runnable() {
                  @Override
                  public void run() {
                      times.add(System.currentTimeMillis());
                  }
              }, 100, 100, TimeUnit.MILLISECONDS);
  
              Thread.sleep(150);
  
              s.drift = -TimeUnit.SECONDS.toNanos(1) - Scheduler.clockDriftTolerance();
  
              Thread.sleep(400);
  
              d.dispose();
  
              Thread.sleep(150);
  
              System.out.println("Runs: " + times.size());
  
              for (int i = 0; i < times.size() - 1 ; i++) {
                  long diff = times.get(i + 1) - times.get(i);
                  System.out.println("Diff #" + i + ": " + diff);
                  assertTrue("" + i + ":" + diff, diff < 150 && diff > 50);
              }
  
              assertTrue("Too few invocations: " + times.size(), times.size() > 2);
  
          } finally {
              w.dispose();
          }
  
      }
  
      @Test
      public void currentTimeDriftForwards() throws Exception {
          CustomDriftScheduler s = new CustomDriftScheduler();
  
          Scheduler.Worker w = s.createWorker();
  
          try {
              final List<Long> times = new ArrayList<>();
  
              Disposable d = w.schedulePeriodically(new Runnable() {
                  @Override
                  public void run() {
                      times.add(System.currentTimeMillis());
                  }
              }, 100, 100, TimeUnit.MILLISECONDS);
  
              Thread.sleep(150);
  
              s.drift = TimeUnit.SECONDS.toNanos(1) + Scheduler.clockDriftTolerance();
  
              Thread.sleep(400);
  
              d.dispose();
  
              Thread.sleep(150);
  
              System.out.println("Runs: " + times.size());
  
              assertTrue(times.size() > 2);
  
              for (int i = 0; i < times.size() - 1 ; i++) {
                  long diff = times.get(i + 1) - times.get(i);
                  System.out.println("Diff #" + i + ": " + diff);
                  assertTrue("Diff out of range: " + diff, diff < 250 && diff > 50);
              }
  
          } finally {
              w.dispose();
          }
  
      }
  }
  