return emptySet();
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    MultisetFeature[] value() default {};

    MultisetFeature[] absent() default {};
  }

  @CollectionSize.Require(ZERO)
  public void testIsEmpty_yes() {
    assertTrue("isEmpty() should return true", collection.isEmpty());
  }

  @CollectionSize.Require(absent = ZERO)
  public void testIsEmpty_no() {
    assertFalse("isEmpty() should return false", collection.isEmpty());
  }

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class ListRetainAllTester<E> extends AbstractListTester<E> {
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testRetainAll_duplicatesKept() {
    E[] array = createSamplesArray();
    array[1] = e0();
    collection = getSubjectGenerator().create(array);
    assertFalse(

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class CollectionForEachTester<E> extends AbstractCollectionTester<E> {
  @CollectionFeature.Require(absent = KNOWN_ORDER)
  public void testForEachUnknownOrder() {
    List<E> elements = new ArrayList<>();
    collection.forEach(elements::add);
    assertEqualIgnoringOrder(asList(createSamplesArray()), elements);
  }

 */
@GwtCompatible
public interface RemovalListener<K, V> {
  /**
   * Notifies the listener that a removal occurred at some point in the past.
   *
   * <p>This does not always signify that the key is now absent from the cache, as it may have
   * already been re-added.
   */
  // Technically should accept RemovalNotification<? extends K, ? extends V>, but because

  public int hashCode() {
    return presentFeatures.hashCode() * 31 + absentFeatures.hashCode();
  }

  @Override
  public String toString() {
    return "{TesterRequirements: present=" + presentFeatures + ", absent=" + absentFeatures + "}";
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

   * either the field is absent or cannot be parsed as a date.
   */
  fun getDate(name: String): Date? = get(name)?.toHttpDateOrNull()

  /**
   * Returns the last value corresponding to the specified field parsed as an HTTP date, or null if
   * either the field is absent or cannot be parsed as a date.
   */

@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class ListRemoveTester<E> extends AbstractListTester<E> {
  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(absent = {ZERO, ONE})
  public void testRemove_duplicate() {
    ArrayWithDuplicate<E> arrayAndDuplicate = createArrayWithDuplicateElement();
    collection = getSubjectGenerator().create(arrayAndDuplicate.elements);

    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    MapFeature[] value() default {};

    MapFeature[] absent() default {};
  }

    }
    assertEquals(
        "A Set's hashCode() should be the sum of those of its elements.",
        expectedHashCode,
        getSet().hashCode());
  }

  @CollectionSize.Require(absent = CollectionSize.ZERO)
  @CollectionFeature.Require(ALLOWS_NULL_VALUES)
  public void testHashCode_containingNull() {
    Collection<E> elements = getSampleElements(getNumElements() - 1);
    int expectedHashCode = 0;