}

  @Override
  protected Map<K, V> makeEmptyMap() {
    throw new UnsupportedOperationException();
  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected final void assertMoreInvariants(Map<K, V> map) {
    BiMap<K, V> bimap = (BiMap<K, V>) map;

    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());

  }

  @Override
  protected Map<K, V> makeEmptyMap() {
    throw new UnsupportedOperationException();
  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected final void assertMoreInvariants(Map<K, V> map) {
    BiMap<K, V> bimap = (BiMap<K, V>) map;

    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());

      }
    }
    return true;
  }

  /**
   * Checks all the properties that should always hold of a map. Also calls {@link
   * #assertMoreInvariants} to check invariants that are peculiar to specific implementations.
   *
   * @see #assertMoreInvariants
   * @param map the map to check.
   */
  protected final void assertInvariants(Map<K, V> map) {
    Set<K> keySet = map.keySet();

  }

  @Override
  protected SortedMap<K, V> makeEmptyMap() {
    throw new UnsupportedOperationException();
  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected void assertMoreInvariants(Map<K, V> map) {
    // TODO: can these be moved to MapInterfaceTest?
    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());
    }

  }

  @Override
  protected Map<K, V> makeEmptyMap() {
    throw new UnsupportedOperationException();
  }

  private static final Joiner JOINER = Joiner.on(", ");

  @Override
  protected final void assertMoreInvariants(Map<K, V> map) {
    // TODO: can these be moved to MapInterfaceTest?
    for (Entry<K, V> entry : map.entrySet()) {
      assertEquals(entry.getKey() + "=" + entry.getValue(), entry.toString());
    }