@CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(ALLOWS_NULL_KEYS)
  public void testEqualsMultimapWithNullKey() {
    Multimap<K, V> original = multimap();
    initMultimapWithNullKey();
    Multimap<K, V> withNull = multimap();
    new EqualsTester()
        .addEqualityGroup(original)
        .addEqualityGroup(
            withNull, getSubjectGenerator().create((Object[]) createArrayWithNullKey()))
        .testEquals();
  }

    } catch (IllegalArgumentException expected) {
    }
  }

  public void testCreateCopy() {
    Table<String, Integer, Character> original =
        create("foo", 1, 'a', "bar", 1, 'b', "foo", 3, 'c');
    Table<String, Integer, Character> copy = HashBasedTable.create(original);
    assertEquals(original, copy);
    assertEquals((Character) 'a', copy.get("foo", 1));
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester

  @Override
  public SampleElements<Object> samples() {
    return new Colliders();
  }

  @Override
  public Object[] createArray(int length) {
    return new Object[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public List<Object> order(List<Object> insertionOrder) {
    return insertionOrder;
  }

  public final String[] createKeyArray(int length) {
    return new String[length];
  }

  @Override
  public final String[] createValueArray(int length) {
    return new String[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public Iterable<Entry<String, String>> order(List<Entry<String, String>> insertionOrder) {
    return insertionOrder;
  }

    return create(array);
  }

  protected abstract Queue<String> create(String[] elements);

  @Override
  public String[] createArray(int length) {
    return new String[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public List<String> order(List<String> insertionOrder) {
    return insertionOrder;
  }

  }

  protected abstract Collection<String> create(String[] elements);

  @Override
  public String[] createArray(int length) {
    return new String[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public List<String> order(List<String> insertionOrder) {
    return insertionOrder;
  }

  @Override
  @SuppressWarnings("unchecked") // generic arrays make typesafety sad
  public Entry<K, V>[] createArray(int length) {
    return (Entry<K, V>[]) new Entry<?, ?>[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public List<Entry<K, V>> order(List<Entry<K, V>> insertionOrder) {
    return insertionOrder;
  }

  public final String[] createKeyArray(int length) {
    return new String[length];
  }

  @Override
  public final String[] createValueArray(int length) {
    return new String[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public Iterable<Entry<String, String>> order(List<Entry<String, String>> insertionOrder) {
    return insertionOrder;
  }

  public final String[] createKeyArray(int length) {
    return new String[length];
  }

  @Override
  public final String[] createValueArray(int length) {
    return new String[length];
  }

  /** Returns the original element list, unchanged. */
  @Override
  public Iterable<Entry<String, String>> order(List<Entry<String, String>> insertionOrder) {
    return insertionOrder;
  }

  }

  private static class BiMapPair<K, V> implements Serializable {
    final BiMap<K, V> forward;
    final BiMap<V, K> backward;

    BiMapPair(BiMap<K, V> original) {
      this.forward = original;
      this.backward = original.inverse();
    }

    private static final long serialVersionUID = 0;
  }

  /**
   * Returns {@link Method} instances for the tests that assume that the inverse will be the same