@GwtCompatible
public enum MultimapFeature implements Feature<Multimap> {
  VALUE_COLLECTIONS_SUPPORT_ITERATOR_REMOVE;

  private final Set<Feature<? super Multimap>> implied;

  MultimapFeature(Feature<? super Multimap>... implied) {
    this.implied = copyToSet(implied);
  }

  @Override
  public Set<Feature<? super Multimap>> getImpliedFeatures() {
    return implied;
  }

    Multimap<String, Integer> multimap = ImmutableSetMultimap.of();
    assertFalse(multimap.containsKey("foo"));
    assertFalse(multimap.containsValue(1));
    assertFalse(multimap.containsEntry("foo", 1));
    assertTrue(multimap.entries().isEmpty());
    assertTrue(multimap.equals(HashMultimap.create()));
    assertEquals(emptySet(), multimap.get("foo"));
    assertEquals(0, multimap.hashCode());
    assertTrue(multimap.isEmpty());

    multimap.put("foo", 3);
    assertTrue(multimap.removeAll("foo") instanceof RandomAccess);
    assertTrue(multimap.removeAll("bar") instanceof RandomAccess);
  }

  /** Confirm that replaceValues() returns a List implementing RandomAccess. */
  public void testReplaceValuesRandomAccess() {
    Multimap<String, Integer> multimap = create();
    multimap.put("foo", 1);
    multimap.put("foo", 3);

    TreeMultimap<@Nullable String, @Nullable Integer> multimap =
        TreeMultimap.create(StringLength.COMPARATOR, DECREASING_INT_COMPARATOR);
    multimap.put("google", 2);
    multimap.put("google", 6);
    multimap.put(null, 3);
    multimap.put(null, 1);
    multimap.put(null, 7);
    multimap.put("tree", 0);
    multimap.put("tree", null);
    return multimap;
  }

    ImmutableMap<String, Integer> map = ImmutableMap.of("one", 1);
    ImmutableSetMultimap<String, Integer> multimap1 = map.asMultimap();
    ImmutableSetMultimap<String, Integer> multimap2 = map.asMultimap();
    assertEquals(1, multimap1.asMap().size());
    assertSame(multimap1, multimap2);
  }

  @J2ktIncompatible
  @GwtIncompatible // NullPointerTester
  public void testNullPointers() {

    int size = getNumElements();

    List<V> values = copyToList(multimap().get(k0()));

    assertTrue(multimap().put(k0(), v1()));
    assertTrue(multimap().put(k0(), v2()));

    values.add(v1());
    values.add(v2());

    assertGet(k0(), values);
    assertEquals(size + 2, multimap().size());
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  public void testPutNullValue_supported() {

    int size = getNumElements();

    List<V> values = copyToList(multimap().get(k0()));

    assertTrue(multimap().put(k0(), v1()));
    assertTrue(multimap().put(k0(), v2()));

    values.add(v1());
    values.add(v2());

    assertGet(k0(), values);
    assertEquals(size + 2, multimap().size());
  }

  @MapFeature.Require({SUPPORTS_PUT, ALLOWS_NULL_VALUES})
  public void testPutNullValue_supported() {

    Collection<V> result = multimap().get(k0());
    assertTrue(result.add(v3()));
    assertTrue(multimap().containsKey(k0()));
    assertEquals(getNumElements() + 1, multimap().size());
    assertTrue(multimap().containsEntry(k0(), v3()));
  }

  @MapFeature.Require(SUPPORTS_PUT)
  public void testPropagatesAddAllToMultimap() {
    Collection<V> result = multimap().get(k0());

    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);
    multimap.put("foo", 3);
    assertEquals(ImmutableSet.of(1, 3), multimap.get("foo"));
    assertEquals(2, multimap.expectedValuesPerKey);
  }

  public void testCreateFromMultimap() {
    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);

    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);
    multimap.put("foo", 3);
    assertEquals(ImmutableSet.of(1, 3), multimap.get("foo"));
    assertEquals(2, multimap.expectedValuesPerKey);
  }

  public void testCreateFromMultimap() {
    HashMultimap<String, Integer> multimap = HashMultimap.create();
    multimap.put("foo", 1);
    multimap.put("bar", 2);