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.internal.operators.observable;
  
  import static org.junit.Assert.assertEquals;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.Mockito.*;
  
  import java.util.List;
  
  import io.reactivex.rxjava3.disposables.Disposable;
  import org.junit.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  import io.reactivex.rxjava3.subjects.PublishSubject;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class ObservableReduceTest extends RxJavaTest {
      Observer<Object> observer;
      SingleObserver<Object> singleObserver;
  
      @Before
      public void before() {
          observer = TestHelper.mockObserver();
          singleObserver = TestHelper.mockSingleObserver();
      }
  
      BiFunction<Integer, Integer, Integer> sum = new BiFunction<Integer, Integer, Integer>() {
          @Override
          public Integer apply(Integer t1, Integer t2) {
              return t1 + t2;
          }
      };
  
      @Test
      public void aggregateAsIntSumObservable() {
  
          Observable<Integer> result = Observable.just(1, 2, 3, 4, 5).reduce(0, sum)
                  .map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  }).toObservable();
  
          result.subscribe(observer);
  
          verify(observer).onNext(1 + 2 + 3 + 4 + 5);
          verify(observer).onComplete();
          verify(observer, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void aggregateAsIntSumSourceThrowsObservable() {
          Observable<Integer> result = Observable.concat(Observable.just(1, 2, 3, 4, 5),
                  Observable.<Integer> error(new TestException()))
                  .reduce(0, sum).map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  }).toObservable();
  
          result.subscribe(observer);
  
          verify(observer, never()).onNext(any());
          verify(observer, never()).onComplete();
          verify(observer, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void aggregateAsIntSumAccumulatorThrowsObservable() {
          BiFunction<Integer, Integer, Integer> sumErr = new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  throw new TestException();
              }
          };
  
          Observable<Integer> result = Observable.just(1, 2, 3, 4, 5)
                  .reduce(0, sumErr).map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  }).toObservable();
  
          result.subscribe(observer);
  
          verify(observer, never()).onNext(any());
          verify(observer, never()).onComplete();
          verify(observer, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void aggregateAsIntSumResultSelectorThrowsObservable() {
  
          Function<Integer, Integer> error = new Function<Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1) {
                  throw new TestException();
              }
          };
  
          Observable<Integer> result = Observable.just(1, 2, 3, 4, 5)
                  .reduce(0, sum).toObservable().map(error);
  
          result.subscribe(observer);
  
          verify(observer, never()).onNext(any());
          verify(observer, never()).onComplete();
          verify(observer, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void backpressureWithNoInitialValueObservable() throws InterruptedException {
          Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
          Observable<Integer> reduced = source.reduce(sum).toObservable();
  
          Integer r = reduced.blockingFirst();
          assertEquals(21, r.intValue());
      }
  
      @Test
      public void backpressureWithInitialValueObservable() throws InterruptedException {
          Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
          Observable<Integer> reduced = source.reduce(0, sum).toObservable();
  
          Integer r = reduced.blockingFirst();
          assertEquals(21, r.intValue());
      }
  
      @Test
      public void aggregateAsIntSum() {
  
          Single<Integer> result = Observable.just(1, 2, 3, 4, 5).reduce(0, sum)
                  .map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  });
  
          result.subscribe(singleObserver);
  
          verify(singleObserver).onSuccess(1 + 2 + 3 + 4 + 5);
          verify(singleObserver, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void aggregateAsIntSumSourceThrows() {
          Single<Integer> result = Observable.concat(Observable.just(1, 2, 3, 4, 5),
                  Observable.<Integer> error(new TestException()))
                  .reduce(0, sum).map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  });
  
          result.subscribe(singleObserver);
  
          verify(singleObserver, never()).onSuccess(any());
          verify(singleObserver, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void aggregateAsIntSumAccumulatorThrows() {
          BiFunction<Integer, Integer, Integer> sumErr = new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  throw new TestException();
              }
          };
  
          Single<Integer> result = Observable.just(1, 2, 3, 4, 5)
                  .reduce(0, sumErr).map(new Function<Integer, Integer>() {
                      @Override
                      public Integer apply(Integer v) {
                          return v;
                      }
                  });
  
          result.subscribe(singleObserver);
  
          verify(singleObserver, never()).onSuccess(any());
          verify(singleObserver, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void aggregateAsIntSumResultSelectorThrows() {
  
          Function<Integer, Integer> error = new Function<Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1) {
                  throw new TestException();
              }
          };
  
          Single<Integer> result = Observable.just(1, 2, 3, 4, 5)
                  .reduce(0, sum).map(error);
  
          result.subscribe(singleObserver);
  
          verify(singleObserver, never()).onSuccess(any());
          verify(singleObserver, times(1)).onError(any(TestException.class));
      }
  
      @Test
      public void backpressureWithNoInitialValue() throws InterruptedException {
          Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
          Maybe<Integer> reduced = source.reduce(sum);
  
          Integer r = reduced.blockingGet();
          assertEquals(21, r.intValue());
      }
  
      @Test
      public void backpressureWithInitialValue() throws InterruptedException {
          Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
          Single<Integer> reduced = source.reduce(0, sum);
  
          Integer r = reduced.blockingGet();
          assertEquals(21, r.intValue());
      }
  
      @Test
      public void reduceWithSingle() {
          Observable.range(1, 5)
          .reduceWith(new Supplier<Integer>() {
              @Override
              public Integer get() throws Exception {
                  return 0;
              }
          }, new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer a, Integer b) throws Exception {
                  return a + b;
              }
          })
          .test()
          .assertResult(15);
      }
  
      @Test
      public void reduceMaybeDoubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeObservableToMaybe(new Function<Observable<Object>, MaybeSource<Object>>() {
              @Override
              public MaybeSource<Object> apply(Observable<Object> o)
                      throws Exception {
                  return o.reduce(new BiFunction<Object, Object, Object>() {
                      @Override
                      public Object apply(Object a, Object b) throws Exception {
                          return a;
                      }
                  });
              }
          });
      }
  
      @Test
      public void reduceMaybeCheckDisposed() {
          TestHelper.checkDisposed(Observable.just(new Object()).reduce(new BiFunction<Object, Object, Object>() {
                      @Override
                      public Object apply(Object a, Object b) throws Exception {
                          return a;
                      }
                  }));
      }
  
      @Test
      public void reduceMaybeBadSource() {
          List<Throwable> errors = TestHelper.trackPluginErrors();
          try {
              new Observable<Object>() {
                  @Override
                  protected void subscribeActual(Observer<? super Object> observer) {
                      observer.onSubscribe(Disposable.empty());
                      observer.onComplete();
                      observer.onNext(1);
                      observer.onError(new TestException());
                      observer.onComplete();
                  }
              }.reduce(new BiFunction<Object, Object, Object>() {
                          @Override
                          public Object apply(Object a, Object b) throws Exception {
                              return a;
                          }
                      })
              .test()
              .assertResult();
  
              TestHelper.assertUndeliverable(errors, 0, TestException.class);
          } finally {
              RxJavaPlugins.reset();
          }
      }
  
      @Test
      public void seedDoubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeObservableToSingle(new Function<Observable<Integer>, SingleSource<Integer>>() {
              @Override
              public SingleSource<Integer> apply(Observable<Integer> o)
                      throws Exception {
                  return o.reduce(0, new BiFunction<Integer, Integer, Integer>() {
                      @Override
                      public Integer apply(Integer a, Integer b) throws Exception {
                          return a;
                      }
                  });
              }
          });
      }
  
      @Test
      public void seedDisposed() {
          TestHelper.checkDisposed(PublishSubject.<Integer>create().reduce(0, new BiFunction<Integer, Integer, Integer>() {
                      @Override
                      public Integer apply(Integer a, Integer b) throws Exception {
                          return a;
                      }
                  }));
      }
  
      @Test
      public void seedBadSource() {
          List<Throwable> errors = TestHelper.trackPluginErrors();
          try {
              new Observable<Integer>() {
                  @Override
                  protected void subscribeActual(Observer<? super Integer> observer) {
                      observer.onSubscribe(Disposable.empty());
                      observer.onComplete();
                      observer.onNext(1);
                      observer.onError(new TestException());
                      observer.onComplete();
                  }
              }
              .reduce(0, new BiFunction<Integer, Integer, Integer>() {
                  @Override
                  public Integer apply(Integer a, Integer b) throws Exception {
                      return a;
                  }
              })
              .test()
              .assertResult(0);
  
              TestHelper.assertUndeliverable(errors, 0, TestException.class);
          } finally {
              RxJavaPlugins.reset();
          }
      }
  }
  