public void testEqualsSameContents() {
    new EqualsTester()
        .addEqualityGroup(
            getMultiset(), getSubjectGenerator().create(getSampleElements().toArray()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  public void testNotEqualsEmpty() {
    new EqualsTester()
        .addEqualityGroup(getMultiset())
        .addEqualityGroup(getSubjectGenerator().create())
        .testEquals();
  }

 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>
 * new EqualsTester()
 *     .addEqualityGroup(new User("page"), new User("page"))
 *     .addEqualityGroup(new User("sergey"))
 *     .testEquals();
 * </pre>
 *
 * <p>This tests:
 *
 * <ul>
 *   <li>comparing each object against itself returns true
 *   <li>comparing each object against null returns false

    new EqualsTester()
        .addEqualityGroup(entry, immutableCell("foo", 1, 'a'))
        .addEqualityGroup(immutableCell("bar", 1, 'a'))
        .addEqualityGroup(immutableCell("foo", 2, 'a'))
        .addEqualityGroup(immutableCell("foo", 1, 'b'))
        .addEqualityGroup(
            Tables.<@Nullable Object, @Nullable Object, @Nullable Object>immutableCell(

    assertThrows(
        NullPointerException.class,
        () -> equalsTester.addEqualityGroup(reference, (Object[]) null));
  }

  /**
   * Test adding objects only by addEqualityGroup, with no reference object specified in the
   * constructor.
   */
  public void testAddEqualObjectWithOArgConstructor() {
    equalsTester.addEqualityGroup(equalObject1, notEqualObject1);
    try {
      equalsTester.testEquals();

    new EqualsTester()
        .addEqualityGroup(original)
        .addEqualityGroup(
            withNull, getSubjectGenerator().create((Object[]) createArrayWithNullValue()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  public void testNotEqualsEmpty() {
    new EqualsTester()
        .addEqualityGroup(multimap())
        .addEqualityGroup(getSubjectGenerator().create())
        .testEquals();

  public void testWrap() {
    new EqualsTester()
        .addEqualityGroup(
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("hello"),
            LENGTH_EQUIVALENCE.wrap("world"))
        .addEqualityGroup(LENGTH_EQUIVALENCE.wrap("hi"), LENGTH_EQUIVALENCE.wrap("yo"))
        .addEqualityGroup(
            LENGTH_EQUIVALENCE.<@Nullable String>wrap(null),

    assertThrows(
        NullPointerException.class,
        () -> equalsTester.addEqualityGroup(reference, (Object[]) null));
  }

  /**
   * Test adding objects only by addEqualityGroup, with no reference object specified in the
   * constructor.
   */
  public void testAddEqualObjectWithOArgConstructor() {
    equalsTester.addEqualityGroup(equalObject1, notEqualObject1);
    try {
      equalsTester.testEquals();

    new EqualsTester()
        .addEqualityGroup(original)
        .addEqualityGroup(
            withNull, getSubjectGenerator().create((Object[]) createArrayWithNullValue()))
        .testEquals();
  }

  @CollectionSize.Require(absent = ZERO)
  public void testNotEqualsEmpty() {
    new EqualsTester()
        .addEqualityGroup(multimap())
        .addEqualityGroup(getSubjectGenerator().create())
        .testEquals();

    new EqualsTester()
        .addEqualityGroup(entry, immutableCell("foo", 1, 'a'))
        .addEqualityGroup(immutableCell("bar", 1, 'a'))
        .addEqualityGroup(immutableCell("foo", 2, 'a'))
        .addEqualityGroup(immutableCell("foo", 1, 'b'))
        .addEqualityGroup(
            Tables.<@Nullable Object, @Nullable Object, @Nullable Object>immutableCell(

        .addEqualityGroup(parse("expireAfterWrite=60m"), parse("expireAfterWrite=1h"))
        .addEqualityGroup(parse("weakKeys"), parse("weakKeys"))
        .addEqualityGroup(parse("softValues"), parse("softValues"))
        .addEqualityGroup(parse("weakValues"), parse("weakValues"))
        .addEqualityGroup(parse("recordStats"), parse("recordStats"))
        .testEquals();