  @Test
  public void testGetDeniedReaders() {

    Acl acl = new Acl.Builder()
        .setReaders(user("AllowedUser1", "AllowedUser2"))
        .setDeniedReaders(group("DeniedGroup"))
        .setOwners(user("AllowedUser1"))
        .build();
    assertEquals(group("DeniedGroup"), acl.getDeniedReaders());
    thrown.expect(UnsupportedOperationException.class);
    acl.getDeniedReaders().addAll(user("DeniedUser"));
  }