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.flowable;
  
  import static org.mockito.ArgumentMatchers.*;
  import static org.mockito.Mockito.*;
  
  import java.util.NoSuchElementException;
  
  import org.junit.*;
  import org.mockito.InOrder;
  import org.reactivestreams.Subscriber;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.functions.Predicate;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class FlowableFirstTest extends RxJavaTest {
  
      Subscriber<String> w;
  
      SingleObserver<Object> wo;
  
      MaybeObserver<Object> wm;
  
      private static final Predicate<String> IS_D = new Predicate<String>() {
          @Override
          public boolean test(String value) {
              return "d".equals(value);
          }
      };
  
      @Before
      public void before() {
          w = TestHelper.mockSubscriber();
          wo = TestHelper.mockSingleObserver();
          wm = TestHelper.mockMaybeObserver();
      }
  
      @Test
      public void firstOrElseOfNoneFlowable() {
          Flowable<String> src = Flowable.empty();
          src.first("default").toFlowable().subscribe(w);
  
          verify(w, times(1)).onNext(anyString());
          verify(w, times(1)).onNext("default");
          verify(w, never()).onError(any(Throwable.class));
          verify(w, times(1)).onComplete();
      }
  
      @Test
      public void firstOrElseOfSomeFlowable() {
          Flowable<String> src = Flowable.just("a", "b", "c");
          src.first("default").toFlowable().subscribe(w);
  
          verify(w, times(1)).onNext(anyString());
          verify(w, times(1)).onNext("a");
          verify(w, never()).onError(any(Throwable.class));
          verify(w, times(1)).onComplete();
      }
  
      @Test
      public void firstOrElseWithPredicateOfNoneMatchingThePredicateFlowable() {
          Flowable<String> src = Flowable.just("a", "b", "c");
          src.filter(IS_D).first("default").toFlowable().subscribe(w);
  
          verify(w, times(1)).onNext(anyString());
          verify(w, times(1)).onNext("default");
          verify(w, never()).onError(any(Throwable.class));
          verify(w, times(1)).onComplete();
      }
  
      @Test
      public void firstOrElseWithPredicateOfSomeFlowable() {
          Flowable<String> src = Flowable.just("a", "b", "c", "d", "e", "f");
          src.filter(IS_D).first("default").toFlowable().subscribe(w);
  
          verify(w, times(1)).onNext(anyString());
          verify(w, times(1)).onNext("d");
          verify(w, never()).onError(any(Throwable.class));
          verify(w, times(1)).onComplete();
      }
  
      @Test
      public void firstFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2, 3).firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(1);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithOneElementFlowable() {
          Flowable<Integer> flowable = Flowable.just(1).firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(1);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithEmptyFlowable() {
          Flowable<Integer> flowable = Flowable.<Integer> empty().firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber).onComplete();
          inOrder.verify(subscriber, never()).onError(any(Throwable.class));
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicateFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2, 3, 4, 5, 6)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(2);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicateAndOneElementFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(2);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicateAndEmptyFlowable() {
          Flowable<Integer> flowable = Flowable.just(1)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement().toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber).onComplete();
          inOrder.verify(subscriber, never()).onError(any(Throwable.class));
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2, 3)
                  .first(4).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(1);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithOneElementFlowable() {
          Flowable<Integer> flowable = Flowable.just(1).first(2).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(1);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithEmptyFlowable() {
          Flowable<Integer> flowable = Flowable.<Integer> empty()
                  .first(1).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(1);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicateFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2, 3, 4, 5, 6)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(8).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(2);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicateAndOneElementFlowable() {
          Flowable<Integer> flowable = Flowable.just(1, 2)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(4).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(2);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicateAndEmptyFlowable() {
          Flowable<Integer> flowable = Flowable.just(1)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(2).toFlowable();
  
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          InOrder inOrder = inOrder(subscriber);
          inOrder.verify(subscriber, times(1)).onNext(2);
          inOrder.verify(subscriber, times(1)).onComplete();
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrElseOfNone() {
          Flowable<String> src = Flowable.empty();
          src.first("default").subscribe(wo);
  
          verify(wo, times(1)).onSuccess(anyString());
          verify(wo, times(1)).onSuccess("default");
          verify(wo, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void firstOrElseOfSome() {
          Flowable<String> src = Flowable.just("a", "b", "c");
          src.first("default").subscribe(wo);
  
          verify(wo, times(1)).onSuccess(anyString());
          verify(wo, times(1)).onSuccess("a");
          verify(wo, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void firstOrElseWithPredicateOfNoneMatchingThePredicate() {
          Flowable<String> src = Flowable.just("a", "b", "c");
          src.filter(IS_D).first("default").subscribe(wo);
  
          verify(wo, times(1)).onSuccess(anyString());
          verify(wo, times(1)).onSuccess("default");
          verify(wo, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void firstOrElseWithPredicateOfSome() {
          Flowable<String> src = Flowable.just("a", "b", "c", "d", "e", "f");
          src.filter(IS_D).first("default").subscribe(wo);
  
          verify(wo, times(1)).onSuccess(anyString());
          verify(wo, times(1)).onSuccess("d");
          verify(wo, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void first() {
          Maybe<Integer> maybe = Flowable.just(1, 2, 3).firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm, times(1)).onSuccess(1);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithOneElement() {
          Maybe<Integer> maybe = Flowable.just(1).firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm, times(1)).onSuccess(1);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithEmpty() {
          Maybe<Integer> maybe = Flowable.<Integer> empty().firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm).onComplete();
          inOrder.verify(wm, never()).onError(any(Throwable.class));
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicate() {
          Maybe<Integer> maybe = Flowable.just(1, 2, 3, 4, 5, 6)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm, times(1)).onSuccess(2);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicateAndOneElement() {
          Maybe<Integer> maybe = Flowable.just(1, 2)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm, times(1)).onSuccess(2);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstWithPredicateAndEmpty() {
          Maybe<Integer> maybe = Flowable.just(1)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .firstElement();
  
          maybe.subscribe(wm);
  
          InOrder inOrder = inOrder(wm);
          inOrder.verify(wm).onComplete();
          inOrder.verify(wm, never()).onError(any(Throwable.class));
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefault() {
          Single<Integer> single = Flowable.just(1, 2, 3)
                  .first(4);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(1);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithOneElement() {
          Single<Integer> single = Flowable.just(1).first(2);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(1);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithEmpty() {
          Single<Integer> single = Flowable.<Integer> empty()
                  .first(1);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(1);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicate() {
          Single<Integer> single = Flowable.just(1, 2, 3, 4, 5, 6)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(8);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(2);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicateAndOneElement() {
          Single<Integer> single = Flowable.just(1, 2)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(4);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(2);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrDefaultWithPredicateAndEmpty() {
          Single<Integer> single = Flowable.just(1)
                  .filter(new Predicate<Integer>() {
                      @Override
                      public boolean test(Integer t1) {
                          return t1 % 2 == 0;
                      }
                  })
                  .first(2);
  
          single.subscribe(wo);
  
          InOrder inOrder = inOrder(wo);
          inOrder.verify(wo, times(1)).onSuccess(2);
          inOrder.verifyNoMoreInteractions();
      }
  
      @Test
      public void firstOrErrorNoElement() {
          Flowable.empty()
              .firstOrError()
              .test()
              .assertNoValues()
              .assertError(NoSuchElementException.class);
      }
  
      @Test
      public void firstOrErrorOneElement() {
          Flowable.just(1)
              .firstOrError()
              .test()
              .assertNoErrors()
              .assertValue(1);
      }
  
      @Test
      public void firstOrErrorMultipleElements() {
          Flowable.just(1, 2, 3)
              .firstOrError()
              .test()
              .assertNoErrors()
              .assertValue(1);
      }
  
      @Test
      public void firstOrErrorError() {
          Flowable.error(new RuntimeException("error"))
              .firstOrError()
              .to(TestHelper.testConsumer())
              .assertNoValues()
              .assertErrorMessage("error")
              .assertError(RuntimeException.class);
      }
  
      @Test
      public void firstOrErrorNoElementFlowable() {
          Flowable.empty()
              .firstOrError()
              .toFlowable()
              .test()
              .assertNoValues()
              .assertError(NoSuchElementException.class);
      }
  
      @Test
      public void firstOrErrorOneElementFlowable() {
          Flowable.just(1)
              .firstOrError()
              .toFlowable()
              .test()
              .assertNoErrors()
              .assertValue(1);
      }
  
      @Test
      public void firstOrErrorMultipleElementsFlowable() {
          Flowable.just(1, 2, 3)
              .firstOrError()
              .toFlowable()
              .test()
              .assertNoErrors()
              .assertValue(1);
      }
  
      @Test
      public void firstOrErrorErrorFlowable() {
          Flowable.error(new RuntimeException("error"))
              .firstOrError()
              .toFlowable()
              .to(TestHelper.testConsumer())
              .assertNoValues()
              .assertErrorMessage("error")
              .assertError(RuntimeException.class);
      }
  }
  