public void testAbsent() {
    assertEquals(
        "Map.merge(absent, value, function) should return value",
        v3(),
        getMap()
            .merge(
                k3(),
                v3(),
                (oldV, newV) -> {
                  throw new AssertionFailedError(
                      "Should not call merge function if key was absent");
                }));
    expectAdded(e3());
  }

  }

  @CollectionSize.Require(absent = ZERO)
  @CollectionFeature.Require(absent = NON_STANDARD_TOSTRING)
  @MapFeature.Require(ALLOWS_NULL_KEYS)
  public void testToStringWithNullKey() {
    initMapWithNullKey();
    testToString_formatting();
  }

  @CollectionSize.Require(absent = ZERO)
  @CollectionFeature.Require(absent = NON_STANDARD_TOSTRING)
  @MapFeature.Require(ALLOWS_NULL_VALUES)

              });
    } catch (UnsupportedOperationException tolerated) {
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  @CollectionSize.Require(absent = ZERO)
  public void testComputeIfPresent_unsupportedPresent() {
    assertThrows(
        UnsupportedOperationException.class, () -> getMap().computeIfPresent(k0(), (k, v) -> v3()));
    expectUnchanged();
  }

  }

  @CollectionSize.Require(absent = ZERO)
  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testRemovePropagatesToMultimap() {
    assertTrue(multimap().entries().remove(mapEntry(k0(), v0())));
    expectMissing(mapEntry(k0(), v0()));
    assertEquals(getNumElements() - 1, multimap().size());
    assertFalse(multimap().containsEntry(k0(), v0()));
  }

  @CollectionSize.Require(absent = ZERO)

  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  public void testEquals_otherMapWithDifferentEntries() {
    Map<K, V> other = newHashMap(getSampleEntries(getNumEntries() - 1));
    other.put(k3(), v3());
    assertFalse(
        "A Map should not equal another Map containing different entries.", getMap().equals(other));
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)

   * {@code Optional.empty}.
   */
  public static <T> Optional<T> absent() {
    return Absent.withType();
  }

  /**
   * Returns an {@code Optional} instance containing the given non-null reference. To have {@code
   * null} treated as {@link #absent}, use {@link #fromNullable} instead.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   *

  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapExclusive() {
    assertFalse(navigableMap.headMap(a.getKey(), false).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testHeadMapInclusive() {
    assertTrue(navigableMap.headMap(a.getKey(), true).containsKey(a.getKey()));
  }

  @CollectionSize.Require(absent = ZERO)
  public void testTailMapExclusive() {

    assertOneToOne();
  }

  @CollectionSize.Require(absent = ZERO)
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testSetCount_oneToOne_removeSupported() {
    assertOneToOne();
  }

  @CollectionSize.Require(absent = ZERO)
  @CollectionFeature.Require(absent = {SUPPORTS_ADD, SUPPORTS_REMOVE})
  public void testSetCount_oneToOne_unsupported() {
    try {
      assertOneToOne();

    expectAdded(e3());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  public void testAdd_unsupportedNotPresent() {
    assertThrows(UnsupportedOperationException.class, () -> collection.add(e3()));
    expectUnchanged();
    expectMissing(e3());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_unsupportedPresent() {
    try {

    expectAdded(e3());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  public void testAdd_unsupportedNotPresent() {
    assertThrows(UnsupportedOperationException.class, () -> collection.add(e3()));
    expectUnchanged();
    expectMissing(e3());
  }

  @CollectionFeature.Require(absent = SUPPORTS_ADD)
  @CollectionSize.Require(absent = ZERO)
  public void testAdd_unsupportedPresent() {
    try {