public static Equivalence<Object> identity() {
    return Identity.INSTANCE;
  }

  static final class Equals extends Equivalence<Object> implements Serializable {

    static final Equals INSTANCE = new Equals();

    @Override
    protected boolean doEquivalent(Object a, Object b) {
      return a.equals(b);
    }

    @Override
    protected int doHash(Object o) {
      return o.hashCode();
    }

    HashCode hashCodeA = HashCode.fromBytes(bytesA);
    HashCode hashCodeB = HashCode.fromBytes(bytesB);

    // They aren't equal...
    assertFalse(hashCodeA.equals(hashCodeB));

    // But they still have the same Object#hashCode() value.
    // Technically not a violation of the equals/hashCode contract, but...?
    assertEquals(hashCodeA.hashCode(), hashCodeB.hashCode());
  }

    /**
     * Compares the specified object with this cell for equality. Two cells are equal when they have
     * equal row keys, column keys, and values.
     */
    @Override
    boolean equals(@CheckForNull Object obj);

    /**
     * Returns the hash code of this cell.
     *
     * <p>The hash code of a table cell is equal to {@link Objects#hashCode}{@code (e.getRowKey(),
     * e.getColumnKey(), e.getValue())}.

        "Two Maps should not be equal if exactly one of them contains a null value.",
        getMap().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerMap() {
    Collection<Entry<K, V>> fewerEntries = getSampleEntries(getNumEntries() - 1);
    assertFalse(
        "Maps of different sizes should not be equal.", getMap().equals(newHashMap(fewerEntries)));
  }

      assertFalse(
          "Should not contain key " + entry.getKey() + " mapped to value " + entry.getValue(),
          equal(getMap().get(entry.getKey()), entry.getValue()));
    }
  }

  private static boolean equal(@Nullable Object a, @Nullable Object b) {
    return a == b || (a != null && a.equals(b));
  }

  // This one-liner saves us from some ugly casts
  protected Entry<K, V> entry(K key, V value) {

    assertFalse(
        "Two Sets should not be equal if exactly one of them contains null.",
        getSet().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerSet() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(fewerElements)));
  }

    assertFalse(
        "Two Sets should not be equal if exactly one of them contains null.",
        getSet().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_smallerSet() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Sets of different sizes should not be equal.",
        getSet().equals(MinimalSet.from(fewerElements)));
  }

        getList().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_shorterList() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Lists of different sizes should not be equal.",
        getList().equals(new ArrayList<E>(fewerElements)));
  }

        // We already know that nodeU equals other.nodeU. Combined with the earlier statement,
        // and the transitive property of equality, this implies that nodeU equals nodeV.
        // If nodeU equals nodeV, condition1 == condition2, so checking condition1 is sufficient.
        return nodeV().equals(other.nodeV());
      }

        getList().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_shorterList() {
    Collection<E> fewerElements = getSampleElements(getNumElements() - 1);
    assertFalse(
        "Lists of different sizes should not be equal.",
        getList().equals(new ArrayList<E>(fewerElements)));
  }