}

  public void testTransform_absent_functionReturnsNull() {
    assertEquals(Optional.absent(), Optional.absent().transform(input -> null));
  }

  public void testEqualsAndHashCode() {
    new EqualsTester()
        .addEqualityGroup(Optional.absent(), reserialize(Optional.absent()))
        .addEqualityGroup(Optional.of(Long.valueOf(5)), reserialize(Optional.of(Long.valueOf(5))))

        VERTICAL_VALUES_PAIRED_STATS.xStats().mean());
    assertThrows(IllegalStateException.class, () -> CONSTANT_VALUES_PAIRED_STATS.leastSquaresFit());
  }

  public void testEqualsAndHashCode() {
    new EqualsTester()
        .addEqualityGroup(
            MANY_VALUES_PAIRED_STATS,
            DUPLICATE_MANY_VALUES_PAIRED_STATS,
            SerializableTester.reserialize(MANY_VALUES_PAIRED_STATS))

    assertThrows(IllegalArgumentException.class, () -> parse(",weakKeys"));

    assertThrows(IllegalArgumentException.class, () -> parse("weakKeys,,softValues"));
  }

  public void testEqualsAndHashCode() {
    new EqualsTester()
        .addEqualityGroup(parse(""), parse(""))
        .addEqualityGroup(parse("concurrencyLevel=7"), parse("concurrencyLevel=7"))

      }
    }
  }

  public abstract static class AbstractFilteredSetTest<C extends Set<Integer>>
      extends AbstractFilteredCollectionTest<C> {
    public void testEqualsAndHashCode() {
      for (List<Integer> contents : SAMPLE_INPUTS) {
        Set<Integer> expected = newHashSet();
        for (Integer i : contents) {
          if (EVEN.apply(i)) {
            expected.add(i);

  /* The names of the expected method that tests equals. */
  private static final ImmutableList<String> EQUALS_TEST_METHOD_NAMES =
      ImmutableList.of(
          "testEquals",
          "testEqualsAndHashCode",
          "testEqualsAndSerializable",
          "testEqualsAndSerialization",
          "testEquality");

  private static final Chopper TEST_SUFFIX =

    assertThrows(IllegalArgumentException.class, () -> parse(",weakKeys"));

    assertThrows(IllegalArgumentException.class, () -> parse("weakKeys,,softValues"));
  }

  public void testEqualsAndHashCode() {
    new EqualsTester()
        .addEqualityGroup(parse(""), parse(""))
        .addEqualityGroup(parse("concurrencyLevel=7"), parse("concurrencyLevel=7"))

        .of(MEGA_STREAM_POPULATION_VARIANCE);
    assertThat(stats.min()).isEqualTo(MEGA_STREAM_MIN);
    assertThat(stats.max()).isEqualTo(MEGA_STREAM_MAX);
  }

  public void testEqualsAndHashCode() {
    new EqualsTester()
        .addEqualityGroup(
            Stats.of(1.0, 1.0, 5.0, 5.0),
            Stats.of(1.0, 1.0, 5.0, 5.0),
            Stats.of(ImmutableList.of(1.0, 1.0, 5.0, 5.0)),

  /* The names of the expected method that tests equals. */
  private static final ImmutableList<String> EQUALS_TEST_METHOD_NAMES =
      ImmutableList.of(
          "testEquals",
          "testEqualsAndHashCode",
          "testEqualsAndSerializable",
          "testEqualsAndSerialization",
          "testEquality");

  private static final Chopper TEST_SUFFIX =