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.flowable;
  
  import org.junit.Test;
  import org.reactivestreams.Publisher;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.flowable.FlowableEventStream.Event;
  import io.reactivex.rxjava3.flowables.GroupedFlowable;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.subscribers.TestSubscriber;
  
  public class FlowableGroupByTests extends RxJavaTest {
  
      @Test
      public void takeUnsubscribesOnGroupBy() {
          Flowable.merge(
              FlowableEventStream.getEventStream("HTTP-ClusterA", 50),
              FlowableEventStream.getEventStream("HTTP-ClusterB", 20)
          )
          // group by type (2 clusters)
          .groupBy(new Function<Event, Object>() {
              @Override
              public Object apply(Event event) {
                  return event.type;
              }
          })
          .take(1)
          .blockingForEach(new Consumer<GroupedFlowable<Object, Event>>() {
              @Override
              public void accept(GroupedFlowable<Object, Event> v) {
                  System.out.println(v);
                  v.take(1).subscribe();  // FIXME groups need consumption to a certain degree to cancel upstream
              }
          });
  
          System.out.println("**** finished");
      }
  
      @Test
      public void takeUnsubscribesOnFlatMapOfGroupBy() {
          Flowable.merge(
              FlowableEventStream.getEventStream("HTTP-ClusterA", 50),
              FlowableEventStream.getEventStream("HTTP-ClusterB", 20)
          )
          // group by type (2 clusters)
          .groupBy(new Function<Event, Object>() {
              @Override
              public Object apply(Event event) {
                  return event.type;
              }
          })
          .flatMap(new Function<GroupedFlowable<Object, Event>, Publisher<Object>>() {
              @Override
              public Publisher<Object> apply(GroupedFlowable<Object, Event> g) {
                  return g.map(new Function<Event, Object>() {
                      @Override
                      public Object apply(Event event) {
                          return event.instanceId + " - " + event.values.get("count200");
                      }
                  });
              }
          })
          .take(20)
          .blockingForEach(new Consumer<Object>() {
              @Override
              public void accept(Object v) {
                  System.out.println(v);
              }
          });
  
          System.out.println("**** finished");
      }
  
      @Test
      public void groupsCompleteAsSoonAsMainCompletes() {
          TestSubscriber<Integer> ts = TestSubscriber.create();
  
          Flowable.range(0, 20)
          .groupBy(new Function<Integer, Integer>() {
              @Override
              public Integer apply(Integer i) {
                  return i % 5;
              }
          })
          .concatMap(new Function<GroupedFlowable<Integer, Integer>, Flowable<Integer>>() {
              @Override
              public Flowable<Integer> apply(GroupedFlowable<Integer, Integer> v) {
                  return v;
              }
          }, 20) // need to prefetch as many groups as groupBy produces to avoid MBE
          .subscribe(ts);
  
          // Behavior change: this now counts as group abandonment because concatMap
          // doesn't subscribe to the 2nd+ emitted groups immediately
          ts.assertValues(
                  0, 5, 10, 15, // First group is okay
                  // any other group gets abandoned so we get 16 one-element group
                  1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19
                  );
          ts.assertComplete();
          ts.assertNoErrors();
      }
  }
  