* For example, "0:0:0:0:0:0:0:1" becomes "::1"
     *
     * @param ipv6Address the IPv6 address string to compress
     * @return the compressed IPv6 address string
     */
    protected static String compressIPv6(final String ipv6Address) {
        if (ipv6Address == null || ipv6Address.isEmpty()) {
            return ipv6Address;
        }

        // Expand :: if present to get full address for normalization

    @Test
    public void testCompressIPv6() {
        // Test IPv6 compression (using reflection to access protected method)
        try {
            java.lang.reflect.Method method = IpAddressUtil.class.getDeclaredMethod("compressIPv6", String.class);
            method.setAccessible(true);

            // Compressed forms should remain unchanged
            assertEquals("::1", method.invoke(null, "::1"));