content: /*
   * Copyright (C) 2020 The Android Open Source Project
   *
   * 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 com.google.android.exoplayer2.util;
  
  import static com.google.common.truth.Truth.assertThat;
  import static org.junit.Assert.assertThrows;
  
  import androidx.test.ext.junit.runners.AndroidJUnit4;
  import java.util.Iterator;
  import java.util.Set;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  
  /** Tests for {@link CopyOnWriteMultiset}. */
  @RunWith(AndroidJUnit4.class)
  public final class CopyOnWriteMultisetTest {
  
    @Test
    public void multipleEqualObjectsCountedAsExpected() {
      String item1 = "a string";
      String item2 = "a string";
      String item3 = "different string";
  
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
  
      multiset.add(item1);
      multiset.add(item2);
      multiset.add(item3);
  
      assertThat(multiset).containsExactly("a string", "a string", "different string");
      assertThat(multiset.elementSet()).containsExactly("a string", "different string");
    }
  
    @Test
    public void removingObjectDecrementsCount() {
      String item1 = "a string";
      String item2 = "a string";
      String item3 = "different string";
  
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
  
      multiset.add(item1);
      multiset.add(item2);
      multiset.add(item3);
  
      multiset.remove("a string");
  
      assertThat(multiset).containsExactly("a string", "different string");
      assertThat(multiset.elementSet()).containsExactly("a string", "different string");
    }
  
    @Test
    public void removingLastObjectRemovesCompletely() {
      String item1 = "a string";
      String item2 = "a string";
      String item3 = "different string";
  
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
  
      multiset.add(item1);
      multiset.add(item2);
      multiset.add(item3);
  
      multiset.remove("different string");
  
      assertThat(multiset).containsExactly("a string", "a string");
      assertThat(multiset.elementSet()).containsExactly("a string");
    }
  
    @Test
    public void removingNonexistentElementSucceeds() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
  
      multiset.remove("a string");
    }
  
    @Test
    public void modifyingIteratorFails() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
      multiset.add("a string");
  
      Iterator<String> iterator = multiset.iterator();
  
      assertThrows(UnsupportedOperationException.class, iterator::remove);
    }
  
    @Test
    public void modifyingElementSetFails() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
      multiset.add("a string");
  
      Set<String> elementSet = multiset.elementSet();
  
      assertThrows(UnsupportedOperationException.class, () -> elementSet.remove("a string"));
    }
  
    @Test
    public void count() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
      multiset.add("a string");
      multiset.add("a string");
  
      assertThat(multiset.count("a string")).isEqualTo(2);
      assertThat(multiset.count("another string")).isEqualTo(0);
    }
  
    @Test
    public void modifyingWhileIteratingElements_succeeds() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
      multiset.add("a string");
      multiset.add("a string");
      multiset.add("another string");
  
      // A traditional collection would throw a ConcurrentModificationException here.
      for (String element : multiset) {
        multiset.remove(element);
      }
  
      assertThat(multiset).isEmpty();
    }
  
    @Test
    public void modifyingWhileIteratingElementSet_succeeds() {
      CopyOnWriteMultiset<String> multiset = new CopyOnWriteMultiset<>();
      multiset.add("a string");
      multiset.add("a string");
      multiset.add("another string");
  
      // A traditional collection would throw a ConcurrentModificationException here.
      for (String element : multiset.elementSet()) {
        multiset.remove(element);
      }
  
      assertThat(multiset).containsExactly("a string");
    }
  }
  