protected M multimap() {
    return multimap;
  }

  /**
   * @return an array of the proper size with {@code null} as the key of the middle element.
   */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();
    Entry<K, V> oldEntry = array[nullKeyLocation];
    array[nullKeyLocation] = mapEntry(null, oldEntry.getValue());

    }
  }

  /** @return an array of the proper size with {@code null} as the key of the middle element. */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();
    Entry<K, V> oldEntry = array[nullKeyLocation];
    array[nullKeyLocation] = entry(null, oldEntry.getValue());

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullKeySupported() {
    initMapWithNullKey();
    expectContents(createArrayWithNullKey());
  }

  @MapFeature.Require(absent = ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullKeyUnsupported() {

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullKeySupported() {
    initMapWithNullKey();
    expectContents(createArrayWithNullKey());
  }

  @MapFeature.Require(absent = ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testCreateWithNullKeyUnsupported() {

    }
  }

  /** @return an array of the proper size with {@code null} as the key of the middle element. */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();
    Entry<K, V> oldEntry = array[nullKeyLocation];
    array[nullKeyLocation] = entry(null, oldEntry.getValue());

    initMapWithNullKey();
    assertEquals(
        "put(present, value) should return the associated value",
        getValueForNullKey(),
        put(newEntry));

    Entry<K, V>[] expected = createArrayWithNullKey();
    expected[getNullLocation()] = newEntry;
    expectContents(expected);
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_KEYS)
  public void testPut_nullKeyUnsupported() {

    Multimap<K, V> withNull = multimap();
    new EqualsTester()
        .addEqualityGroup(original)
        .addEqualityGroup(
            withNull, getSubjectGenerator().create((Object[]) createArrayWithNullKey()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(ALLOWS_NULL_VALUES)
  public void testEqualsMultimapWithNullValue() {
    Multimap<K, V> original = multimap();

    Multimap<K, V> withNull = multimap();
    new EqualsTester()
        .addEqualityGroup(original)
        .addEqualityGroup(
            withNull, getSubjectGenerator().create((Object[]) createArrayWithNullKey()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(ALLOWS_NULL_VALUES)
  public void testEqualsMultimapWithNullValue() {
    Multimap<K, V> original = multimap();

  }

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testForEach_nullKeys() {
    initMapWithNullKey();
    List<Entry<K, V>> expectedEntries = asList(createArrayWithNullKey());
    List<Entry<K, V>> entries = new ArrayList<>();
    getMap().forEach((k, v) -> entries.add(entry(k, v)));
    assertEqualIgnoringOrder(expectedEntries, entries);
  }

  }

  @MapFeature.Require(ALLOWS_NULL_KEYS)
  @CollectionSize.Require(absent = ZERO)
  public void testForEach_nullKeys() {
    initMapWithNullKey();
    List<Entry<K, V>> expectedEntries = asList(createArrayWithNullKey());
    List<Entry<K, V>> entries = new ArrayList<>();
    getMap().forEach((k, v) -> entries.add(entry(k, v)));
    Helpers.assertEqualIgnoringOrder(expectedEntries, entries);
  }