throw new UnsupportedOperationException();
  }

  /**
   * Not supported. <b>You are attempting to create a map that may contain a non-{@code Comparable}
   * key.</b> Proper calls will resolve to the version in {@code ImmutableSortedMap}, not this dummy
   * version.
   *
   * @throws UnsupportedOperationException always
   * @deprecated <b>Pass a key of type {@code Comparable} to use {@link

   * order of those futures, test that various get calls (timed before future completion, untimed
   * before future completion, and untimed after future completion) return or throw the proper
   * values.
   */
  @J2ktIncompatible
  @GwtIncompatible // used only in GwtIncompatible tests
  private static void runExtensiveMergerTest(Merger merger) throws InterruptedException {

  protected void expectMissingValues(V... elements) {
    for (V element : elements) {
      assertFalse("Should not contain value " + element, getMap().containsValue(element));
    }
  }

  /** @return an array of the proper size with {@code null} as the key of the middle element. */
  protected Entry<K, V>[] createArrayWithNullKey() {
    Entry<K, V>[] array = createSamplesArray();
    int nullKeyLocation = getNullLocation();

    throw new UnsupportedOperationException();
  }

  /**
   * Not supported. <b>You are attempting to create a set that may contain a non-{@code Comparable}
   * element.</b> Proper calls will resolve to the version in {@code ImmutableSortedSet}, not this
   * dummy version.
   *
   * @throws UnsupportedOperationException always

 *   <li>remove();
 *   <li>next();
 * </ol>
 *
 * <p>This particular order of operations may be unrealistic, and testing all 3^5 of them may be
 * thought of as overkill; however, it's difficult to determine which proper subset of this massive
 * set would be sufficient to expose any possible bug. Brute force is simpler.
 *
 * <p>To use this class the concrete subclass must implement the {@link

   * collection is empty, but we'd still like to test removeAll(null) when we
   * can. We split the test into empty and non-empty cases. This allows us to
   * suppress only the former.
   */

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)
  public void testRemoveAll_nullCollectionReferenceEmptySubject() {
    try {
      collection.removeAll(null);

    private ArrayWithDuplicate(E[] elements, E duplicate) {
      this.elements = elements;
      this.duplicate = duplicate;
    }
  }

  /**
   * @return an array of the proper size with a duplicate element. The size must be at least three.
   */
  protected ArrayWithDuplicate<E> createArrayWithDuplicateElement() {
    E[] elements = createSamplesArray();

   * collection is empty, but we'd still like to test retainAll(null) when we
   * can. We split the test into empty and non-empty cases. This allows us to
   * suppress only the former.
   */

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  @CollectionSize.Require(ZERO)
  public void testRetainAll_nullCollectionReferenceEmptySubject() {
    try {
      collection.retainAll(null);

       * ClassNotFoundException thereafter.
       *
       * Android API level 26 and JVM8 both let our Error propagate directly the first time and
       * throw NoClassDefFoundError thereafter. This is the proper behavior according to the spec.
       * See https://docs.oracle.com/javase/specs/jls/se8/html/jls-12.html#jls-12.4.2 (steps #11 and
       * #5).
       *

/** Unit test for {@link Streams}. */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class StreamsTest extends TestCase {
  /*
   * Full and proper black-box testing of a Stream-returning method is extremely involved, and is
   * overkill when nearly all Streams are produced using well-tested JDK calls. So, we cheat and
   * just test that the toArray() contents are as expected.