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.junit.Assert.assertEquals;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.Mockito.*;
  
  import java.util.Arrays;
  import java.util.concurrent.TimeUnit;
  
  import org.junit.Test;
  import org.mockito.InOrder;
  import org.reactivestreams.Subscriber;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  import io.reactivex.rxjava3.subscribers.TestSubscriber;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class FlowableSkipLastTest extends RxJavaTest {
  
      @Test
      public void skipLastEmpty() {
          Flowable<String> flowable = Flowable.<String> empty().skipLast(2);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          verify(subscriber, never()).onNext(any(String.class));
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void skipLast1() {
          Flowable<String> flowable = Flowable.fromIterable(Arrays.asList("one", "two", "three")).skipLast(2);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          InOrder inOrder = inOrder(subscriber);
          flowable.subscribe(subscriber);
  
          inOrder.verify(subscriber, never()).onNext("two");
          inOrder.verify(subscriber, never()).onNext("three");
          verify(subscriber, times(1)).onNext("one");
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void skipLast2() {
          Flowable<String> flowable = Flowable.fromIterable(Arrays.asList("one", "two")).skipLast(2);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          verify(subscriber, never()).onNext(any(String.class));
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void skipLastWithZeroCount() {
          Flowable<String> w = Flowable.just("one", "two");
          Flowable<String> flowable = w.skipLast(0);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          flowable.subscribe(subscriber);
  
          verify(subscriber, times(1)).onNext("one");
          verify(subscriber, times(1)).onNext("two");
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void skipLastWithBackpressure() {
          Flowable<Integer> f = Flowable.range(0, Flowable.bufferSize() * 2).skipLast(Flowable.bufferSize() + 10);
          TestSubscriber<Integer> ts = new TestSubscriber<>();
          f.observeOn(Schedulers.computation()).subscribe(ts);
          ts.awaitDone(5, TimeUnit.SECONDS);
          ts.assertNoErrors();
          assertEquals((Flowable.bufferSize()) - 10, ts.values().size());
  
      }
  
      @Test(expected = IllegalArgumentException.class)
      public void skipLastWithNegativeCount() {
          Flowable.just("one").skipLast(-1);
      }
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(Flowable.just(1).skipLast(1));
      }
  
      @Test
      public void error() {
          Flowable.error(new TestException())
          .skipLast(1)
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeFlowable(new Function<Flowable<Object>, Flowable<Object>>() {
              @Override
              public Flowable<Object> apply(Flowable<Object> f)
                      throws Exception {
                  return f.skipLast(1);
              }
          });
      }
  
  }
  