int INITIAL_COUNT = 14;
    when(backingMap.get(KEY)).thenReturn(new AtomicInteger(INITIAL_COUNT));

    assertEquals(INITIAL_COUNT, multiset.remove(KEY, 0));
  }

  public void testRemove_zeroFromNone() {
    when(backingMap.get(KEY)).thenReturn(null);

    assertEquals(0, multiset.remove(KEY, 0));
  }

  public void testRemove_nonePresent() {
    when(backingMap.get(KEY)).thenReturn(null);