*
 * <p>As with {@code Map}, the behavior of a {@code Multimap} is not specified if key objects
 * already present in the multimap change in a manner that affects {@code equals} comparisons. Use
 * caution if mutable objects are used as keys in a {@code Multimap}.
 *
 * <p>All methods that modify the multimap are optional. The view collections returned by the

      Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

      Multimap<K, V> synchronizedMultimap(Multimap<K, V> multimap) {
    return Synchronized.multimap(multimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified multimap. Query operations on the returned
   * multimap "read through" to the specified multimap, and attempts to modify the returned
   * multimap, either directly or through the multimap's views, result in an {@code

  }

  @MapFeature.Require({SUPPORTS_PUT, SUPPORTS_REMOVE})
  public void testReplaceValuesWithDuplicates() {
    int size = multimap().size();
    List<V> oldValues = new ArrayList<>(multimap().get(k0()));
    List<V> values = asList(v0(), v3(), v0());
    assertEquals(oldValues, new ArrayList<V>(multimap().replaceValues(k0(), values)));

    extends AbstractMultimapTester<K, V, Multimap<K, V>> {

  public void testSize() {
    int expectedSize = getNumElements();
    Multimap<K, V> multimap = multimap();
    assertEquals(expectedSize, multimap.size());

    int size = 0;
    for (Entry<K, V> entry : multimap.entries()) {
      assertTrue(multimap.containsEntry(entry.getKey(), entry.getValue()));
      size++;
    }

        NullPointerException.class, () -> multimap().putAll(k3(), newArrayList(v3(), null)));

    Collection<V> values = multimap().get(k3());
    if (values.size() == 0) {
      expectUnchanged();
      // Be extra thorough in case internal state was corrupted by the expected null.
      assertEquals(new ArrayList<>(), new ArrayList<>(values));
      assertEquals(size, multimap().size());
    } else {

  }

  public void testKeysElementSet() {
    assertEquals(multimap().keySet(), multimap().keys().elementSet());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeysRemove() {
    int original = multimap().keys().remove(k0(), 1);
    assertEquals(max(original - 1, 0), multimap().get(k0()).size());
  }

  @CollectionSize.Require(ONE)

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MultimapContainsEntryTester<K, V>
    extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  @CollectionSize.Require(absent = ZERO)
  public void testContainsEntryYes() {
    assertTrue(multimap().containsEntry(k0(), v0()));
  }

  public void testContainsEntryNo() {
    assertFalse(multimap().containsEntry(k3(), v3()));
  }

  public void testContainsEntryAgreesWithGet() {

  public void testPutDuplicateValue() {
    List<Entry<K, V>> entries = copyToList(multimap().entries());

    for (Entry<K, V> entry : entries) {
      resetContainer();

      K k = entry.getKey();
      V v = entry.getValue();

      List<V> values = multimap().get(k);
      List<V> expectedValues = copyToList(values);

      assertTrue(multimap().put(k, v));
      expectedValues.add(v);
      assertGet(k, expectedValues);

    if (multimap.isEmpty() && valueComparator == null) {
      return of();
    }

    if (multimap instanceof ImmutableSetMultimap) {
      @SuppressWarnings("unchecked") // safe since multimap is not writable
      ImmutableSetMultimap<K, V> kvMultimap = (ImmutableSetMultimap<K, V>) multimap;
      if (!kvMultimap.isPartialView()) {
        return kvMultimap;
      }
    }