assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    counter.write(0);
    written += 1;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    byte[] data = new byte[10];
    counter.write(data);
    written += 10;
    assertEquals(written, out.size());
    assertEquals(written, counter.getCount());

    counter.write(data, 0, 5);
    written += 5;

    Multiset.Entry<E> entry = getOnlyElement(getMultiset().entrySet());
    assertEquals(3, entry.getCount());
    assertTrue(getMultiset().remove(e0()));
    assertEquals(2, entry.getCount());
    assertTrue(getMultiset().elementSet().remove(e0()));
    assertEquals(0, entry.getCount());
    getMultiset().add(e0(), 2);
    assertEquals(2, entry.getCount());
  }

  public void testToString() {

    Multiset.Entry<E> entry = getOnlyElement(getMultiset().entrySet());
    assertEquals(3, entry.getCount());
    assertTrue(getMultiset().remove(e0()));
    assertEquals(2, entry.getCount());
    assertTrue(getMultiset().elementSet().remove(e0()));
    assertEquals(0, entry.getCount());
    getMultiset().add(e0(), 2);
    assertEquals(2, entry.getCount());
  }

  public void testToString() {

    assertEquals(3, counter.getCount());
  }

  public void testSkip() throws IOException {
    assertEquals(10, counter.skip(10));
    assertEquals(10, counter.getCount());
  }

  public void testSkipEOF() throws IOException {
    assertEquals(20, counter.skip(30));
    assertEquals(20, counter.getCount());
    assertEquals(0, counter.skip(20));
    assertEquals(20, counter.getCount());

    this.offset = offset;
    this.length = length;
  }

  private int getCount(int index) {
    return (int) (cumulativeCounts[offset + index + 1] - cumulativeCounts[offset + index]);
  }

  @Override
  Entry<E> getEntry(int index) {
    return Multisets.immutableEntry(elementSet.asList().get(index), getCount(index));
  }

  @Override
  @CheckForNull
  public Entry<E> firstEntry() {

    assertEquals(1, listenerLatch.getCount());
    assertFalse(task.isDone());
    assertFalse(task.isCancelled());

    // Start the task to put it in the RUNNING state.  Have to use a separate
    // thread because the task will block on the task latch after unblocking
    // the run latch.
    exec.execute(task);
    runLatch.await();
    assertEquals(1, listenerLatch.getCount());
    assertFalse(task.isDone());

    assertEquals(1, listenerLatch.getCount());
    assertFalse(task.isDone());
    assertFalse(task.isCancelled());

    // Start the task to put it in the RUNNING state.  Have to use a separate
    // thread because the task will block on the task latch after unblocking
    // the run latch.
    exec.execute(task);
    runLatch.await();
    assertEquals(1, listenerLatch.getCount());
    assertFalse(task.isDone());

    if (!entryIterator.hasNext()) {
      return null;
    }
    Entry<E> entry = entryIterator.next();
    return Multisets.immutableEntry(entry.getElement(), entry.getCount());
  }

  @Override
  @CheckForNull
  public Entry<E> lastEntry() {
    return delegate().lastEntry();
  }

  /**
   * A sensible definition of {@link #lastEntry()} in terms of {@code

    }

    @Override
    public int count(@Nullable Object element) {
      for (Entry<E> entry : entrySet()) {
        if (Objects.equal(entry.getElement(), element)) {
          return entry.getCount();
        }
      }
      return 0;
    }

    @Override
    public int add(E element, int occurrences) {
      checkArgument(occurrences >= 0);
      Integer frequency = backingMap.get(element);

            crawler1.awaitTermination();
            crawler2.awaitTermination();

            assertEquals(maxCount, dataService.getCount(sessionId1));
            assertEquals(maxCount, dataService.getCount(sessionId2));

            UrlQueue urlQueue;
            while ((urlQueue = urlQueueService.poll(sessionId1)) != null) {