// let computation complete
    letGetFinishSignal.countDown();
    getFinishedSignal.await();
    checkNothingLogged();

    // asMap view should have been updated
    assertEquals(2, cache.size());
    assertEquals(getKey + suffix, map.get(getKey));
    assertEquals(refreshKey + suffix, map.get(refreshKey));
  }

  /**
   * Computes the function of current and new value. Subclasses should open-code this update
   * function for most uses, but the virtualized form is needed within retryUpdate.
   *
   * @param currentValue the current value (of either base or a cell)
   * @param newValue the argument from a user update call
   * @return result of the update function
   */
  abstract long fn(long currentValue, long newValue);

  /**

  /** Updates this hasher with the given byte. */
  protected abstract void update(byte b);

  /** Updates this hasher with the given bytes. */
  protected void update(byte[] b) {
    update(b, 0, b.length);
  }

  /** Updates this hasher with {@code len} bytes starting at {@code off} in the given buffer. */
  protected void update(byte[] b, int off, int len) {

    assertThat(c.asMap().computeIfAbsent("hash-2", k -> "")).isEqualTo("");
  }

  public void testComputeIfPresent() {
    cache.put(key, "1");
    // simultaneous update for same key, expect count successful updates
    doParallelCacheOp(
        count,
        n -> {
          cache.asMap().computeIfPresent(key, (k, v) -> v + delimiter + n);
        });
    assertEquals(1, cache.size());

        AbstractFuture<?> future, @CheckForNull Waiter expect, @CheckForNull Waiter update) {
      return waitersUpdater.compareAndSet(future, expect, update);
    }

    @Override
    boolean casListeners(AbstractFuture<?> future, @CheckForNull Listener expect, Listener update) {
      return listenersUpdater.compareAndSet(future, expect, update);
    }

    /** Performs a GAS operation on the {@link #listeners} field. */

  private class TestHasher extends AbstractByteHasher {

    private final ByteArrayOutputStream out = new ByteArrayOutputStream();

    @Override
    protected void update(byte b) {
      out.write(b);
    }

    @Override
    protected void update(byte[] b, int off, int len) {
      out.write(b, off, len);
    }

    byte[] bytes() {
      return out.toByteArray();
    }

 * views are modifiable.
 *
 * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent
 * read operations will work correctly if the last write <i>happens-before</i> any reads. To allow
 * concurrent update operations, wrap your multimap with a call to {@link
 * Multimaps#synchronizedSetMultimap}.
 *

 * implement {@link java.util.RandomAccess}.
 *
 * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent
 * read operations will work correctly. To allow concurrent update operations, wrap your multimap
 * with a call to {@link Multimaps#synchronizedListMultimap}.
 *
 * <p>See the Guava User Guide article on <a href=

    assertThat(setToTest).isEqualTo(wrappedSet);
    assertThat(setToTest).isEqualTo(copyOfWrappedSet);

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

    ImmutableSet<Integer> copyOfModifiedSet = ImmutableSet.copyOf(wrappedSet); // {2,3}
    // sanity check on construction of copyOfModifiedSet

    assertThat(setToTest).isEqualTo(wrappedSet);
    assertThat(setToTest).isEqualTo(copyOfWrappedSet);

    // invalidate setToTest
    wrappedSet.remove(1);
    // sanity check on update of wrappedSet
    assertThat(wrappedSet).isNotEqualTo(copyOfWrappedSet);

    ImmutableSet<Integer> copyOfModifiedSet = ImmutableSet.copyOf(wrappedSet); // {2,3}
    // sanity check on construction of copyOfModifiedSet