when {
      value != null -> LinkedTags(key, value, this)
      else -> this
    }

  override fun <T : Any> get(key: KClass<T>): T? = null

  override fun toString() = "{}"
}

/**
 * An invariant of this implementation is that [next] must not contain a mapping for [key].
 * Otherwise, we would have two values for the same key.
 */
private class LinkedTags<K : Any>(
  private val key: KClass<K>,

    assertFalse(entrySet.contains("foo"));
  }

  /**
   * Override this to check invariants which should hold true for a particular implementation, but
   * which are not generally applicable to every instance of Map.
   *
   * @param map the map whose additional invariants to check.
   */
  protected void assertMoreInvariants(Map<K, V> map) {}

  public void testClear() {
    Map<K, V> map;

   *
   * <p>Normally this method leaves the elements at up to {@code index - 1}, inclusive, untouched.
   * Under these circumstances, it returns {@code null}.
   *
   * <p>Occasionally, in order to maintain the heap invariant, it must swap a later element of the
   * list with one before {@code index}. Under these circumstances it returns a pair of elements as

  protected Entry<K, V> entry(K key, V value) {
    return mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    // TODO: move this to invariant checks once the appropriate hook exists?
    super.expectContents(expected);
    for (Entry<K, V> entry : expected) {
      assertEquals(

  protected Entry<K, V> entry(K key, V value) {
    return mapEntry(key, value);
  }

  @Override
  protected void expectContents(Collection<Entry<K, V>> expected) {
    // TODO: move this to invariant checks once the appropriate hook exists?
    super.expectContents(expected);
    for (Entry<K, V> entry : expected) {
      assertEquals(

    // These compound characters map their its components.
    assertThat("¼".map()).isEqualTo("1⁄4")
    assertThat("™".map()).isEqualTo("tm")
  }

  /** Confirm the compact table satisfies is documented invariants. */
  @Test fun validateCompactTableInvariants() {
    // Less than 16,834 bytes, because we binary search on a 14-bit index.
    assertThat(compactTable.sections.length).isLessThan(1 shl 14)

    assertFalse(entrySet.contains("foo"));
  }

  /**
   * Override this to check invariants which should hold true for a particular implementation, but
   * which are not generally applicable to every instance of Map.
   *
   * @param map the map whose additional invariants to check.
   */
  protected void assertMoreInvariants(Map<K, V> map) {}

  public void testClear() {
    Map<K, V> map;

      return null; // Wrong number of parts
    }

    byte[] bytes = new byte[IPV4_PART_COUNT];
    int start = 0;
    // Iterate through the parts of the ip string.
    // Invariant: start is always the beginning of an octet.
    for (int i = 0; i < IPV4_PART_COUNT; i++) {
      int end = ipString.indexOf(IPV4_DELIMITER, start);
      if (end == -1) {
        end = ipString.length();
      }

      // before the cancelled future completes, it will synchronously complete both the newFuture
      // from the cancelled operation and its own. This can cause one runnable to queue two tasks,
      // breaking the invariant this method relies on to iteratively run the next task after the
      // previous one completes.
      if (get() == RunningState.CANCELLED) {
        delegate = null;
        sequencer = null;
        return;

    )

    taskFaker.assertNoMoreTasks()
  }

  /**
   * This test puts several connections in flight that all fail at approximately the same time. It
   * confirms the fast fallback implements these invariants:
   *
   *  * if there's no TCP connect in flight, start one.
   *  * don't start a new TCP connect within 250 ms of the previous TCP connect.
   */
  @Test
  fun minimumDelayEnforcedBetweenConnects() {