* depend on the element values, such as a {@link SortedSet}, or on the insertion ordering, such
   * as a {@link LinkedHashSet}. All list tests and sorted-collection tests automatically specify
   * this feature.
   */
  KNOWN_ORDER,

  /**
   * Indicates that a collection has a different {@link Object#toString} representation than most

/**
 * Implementation of {@link ImmutableSet} with two or more elements.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class RegularImmutableSet<E> extends ImmutableSet<E> {
  private static final Object[] EMPTY_ARRAY = new Object[0];

import java.util.Comparator;
import javax.annotation.CheckForNull;

/**
 * An immutable sorted multiset with one or more distinct elements.
 *
 * @author Louis Wasserman
 */
@SuppressWarnings("serial") // uses writeReplace, not default serialization
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class RegularImmutableSortedMultiset<E> extends ImmutableSortedMultiset<E> {

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Bimap with zero or more mappings.
 *
 * @author Louis Wasserman
 */
@GwtCompatible(serializable = true, emulated = true)
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
@ElementTypesAreNonnullByDefault
final class RegularImmutableBiMap<K, V> extends ImmutableBiMap<K, V> {

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@link AbstractMultiset}.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 */
@SuppressWarnings("serial") // No serialization is used in this test
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class SimpleAbstractMultisetTest extends TestCase {
  @J2ktIncompatible
  @GwtIncompatible // suite

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@link AbstractMultiset}.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 */
@SuppressWarnings("serial") // No serialization is used in this test
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class SimpleAbstractMultisetTest extends TestCase {
  @J2ktIncompatible
  @GwtIncompatible // suite

import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@code AbstractIterator}.
 *
 * @author Kevin Bourrillion
 */
@SuppressWarnings("serial") // No serialization is used in this test
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class AbstractIteratorTest extends TestCase {

  public void testDefaultBehaviorOfNextAndHasNext() {

import junit.framework.Test;
import junit.framework.TestSuite;

/**
 * Generates a test suite covering the {@link Set} implementations in the {@link java.util} package.
 * Can be subclassed to specify tests that should be suppressed.
 *
 * @author Kevin Bourrillion
 */
@GwtIncompatible
public class TestsForSetsInJavaUtil {
  public static Test suite() {
    return new TestsForSetsInJavaUtil().allTests();
  }

import junit.framework.Test;
import junit.framework.TestSuite;

/**
 * Generates a test suite covering the {@link Map} implementations in the {@link java.util} package.
 * Can be subclassed to specify tests that should be suppressed.
 *
 * @author Kevin Bourrillion
 */
@GwtIncompatible
public class TestsForMapsInJavaUtil {

  public static Test suite() {
    return new TestsForMapsInJavaUtil().allTests();

  public ImmutableMultiset<K> keys() {
    return (ImmutableMultiset<K>) super.keys();
  }

  @Override
  ImmutableMultiset<K> createKeys() {
    return new Keys();
  }

  @SuppressWarnings("serial") // Uses writeReplace, not default serialization
  @WeakOuter
  class Keys extends ImmutableMultiset<K> {
    @Override
    public boolean contains(@CheckForNull Object object) {
      return containsKey(object);