map.put("quux", "quux");
    assertFalse(map.values() instanceof Set);
    assertTrue(map.values().removeAll(ImmutableSet.of("bar")));
    assertEquals(1, map.size());
  }

  public void testComputeIfAbsent_RemovalListener() {
    List<RemovalNotification<Object, Object>> notifications = new ArrayList<>();
    RemovalListener<Object, Object> removalListener =
        new RemovalListener<Object, Object>() {