when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existing);

    // another map.get()
    when(backingMap.get(KEY)).thenReturn(existing);
    // we shouldn't see any more map operations; CHM will now just update the AtomicInteger

    assertEquals(12, multiset.add(KEY, 3));
    assertEquals(15, existing.get());
  }

  public void testRemove_zeroFromSome() {
    final int INITIAL_COUNT = 14;

    when(backingMap.putIfAbsent(eq(KEY), isA(AtomicInteger.class))).thenReturn(existing);

    // another map.get()
    when(backingMap.get(KEY)).thenReturn(existing);
    // we shouldn't see any more map operations; CHM will now just update the AtomicInteger

    assertEquals(12, multiset.add(KEY, 3));
    assertEquals(15, existing.get());
  }

  public void testRemove_zeroFromSome() {
    final int INITIAL_COUNT = 14;

application/pdf=pdf\n\
application/x-fictionbook+xml=fb2\n\
application/e-pub+zip=epub\n\
application/x-ibooks+zip=ibooks\n\
text/plain=txt\n\
application/rtf=rtf\n\
application/vnd.ms-htmlhelp=chm\n\
application/zip=zip\n\
application/x-7z-comressed=7z\n\
application/x-bzip=bz\n\
application/x-bzip2=bz2\n\
application/x-tar=tar\n\
application/x-rar-compressed=rar\n\
video/3gp=3gp\n\
video/3g2=3g2\n\