void testConstructor_EmptyToken() {
        // 1. GIVEN
        byte[] emptyToken = new byte[0];
        Map<Integer, KerberosKey> keys = new HashMap<>();

        // 2. WHEN & 3. THEN
        // When ASN1InputStream.readObject() returns null due to empty input,
        // ASN1Util.as() throws NullPointerException (not wrapped)
        Exception exception = assertThrows(Exception.class, () -> {