StringSubscriber s2 = new StringSubscriber();
    ObjectSubscriber o1 = new ObjectSubscriber();

    Iterator<Subscriber> empty = registry.getSubscribers("");
    assertFalse(empty.hasNext());

    empty = registry.getSubscribers("");

    registry.register(s1);
    assertFalse(empty.hasNext());

    Iterator<Subscriber> one = registry.getSubscribers("");
    assertEquals(s1, one.next().target);

		return err
	}
	if (!r.Filter.Tag.IsEmpty() || len(r.Filter.And.Tags) != 0) && !r.DelMarkerExpiration.Empty() {
		return errInvalidRuleDelMarkerExpiration
	}
	if !r.Expiration.set && !r.Transition.set && !r.NoncurrentVersionExpiration.set && !r.NoncurrentVersionTransition.set && r.DelMarkerExpiration.Empty() {
		return errXMLNotWellFormed
	}
	return nil
}

    }

    @Test
    @DisplayName("byte[] ctor: empty token throws PACDecodingException with clear message")
    void byteArrayConstructor_emptyToken_throws() {
        // Arrange
        byte[] empty = new byte[0];

        // Act + Assert
        PACDecodingException ex = assertThrows(PACDecodingException.class, () -> new KerberosApRequest(empty, new KerberosKey[0]));

    }

    default void setDefaultLabelValue(final String value) {
        setSystemProperty(Constants.DEFAULT_LABEL_VALUE_PROPERTY, value);
        propMap.remove(DEFAULT_LABEL_VALUES);
    }

    default String getDefaultLabelValue() {
        return getSystemProperty(Constants.DEFAULT_LABEL_VALUE_PROPERTY, StringUtil.EMPTY);
    }

    }

    /**
     * Test contains method with empty list
     */
    @Test
    @DisplayName("Contains should return false for empty list")
    void testContainsEmptyList() {
        List<AvPair> emptyList = new ArrayList<>();
        assertFalse(AvPairs.contains(emptyList, AvPair.MsvAvFlags), "Should return false for empty list");
    }

    /**
     * Test contains method with existing type

    /**
     * An empty string <code>""</code>.
     */
    public static final String EMPTY = "";

    /**
     * An empty array of strings.
     */
    public static final String[] EMPTY_STRINGS = new String[0];


    /**
     * Checks if the string is empty or null.
     *
     * @param text the string to check
     * @return true if empty or null, false otherwise
     */

    }

    @Test
    void isDotQuadIPHandlesEmptyString() {
        // Empty string should return false, not throw exception
        assertFalse(UniAddress.isDotQuadIP(""), "isDotQuadIP should return false for empty string");
    }

    @ParameterizedTest
    @ValueSource(strings = { "123456", "007", "999" })

    }

    @Test
    @DisplayName("Test PacDataInputStream readString with empty string")
    void testReadEmptyString() throws Exception {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);

        // Write an empty string structure
        writeLittleEndianInt(dos, 0); // totalChars

  }

  private static final Map<Integer, Integer> EMPTY = emptyMap();
  private static final Map<Integer, Integer> SINGLETON = singletonMap(1, 2);

  public void testMapDifferenceEmptyEmpty() {
    MapDifference<Integer, Integer> diff = Maps.difference(EMPTY, EMPTY);
    assertTrue(diff.areEqual());
    assertEquals(EMPTY, diff.entriesOnlyOnLeft());
    assertEquals(EMPTY, diff.entriesOnlyOnRight());

        // Verify num_sids
        assertEquals(0, lsarSidArrayX.num_sids, "num_sids should be 0 for an empty array");

        // Verify sids array
        assertNotNull(lsarSidArrayX.sids, "sids array should not be null for an empty array");
        assertEquals(0, lsarSidArrayX.sids.length, "sids array length should be 0 for an empty array");
    }

    @Test
    void testConstructorWithNullSIDArray() {
        jcifs.SID[] sids = null;