assertTrue(ex.getMessage().contains("Invalid kerberos request"));
    }

    @Test
    @DisplayName("seq ctor: unknown field tag causes failure")
    void sequenceConstructor_unknownField_throws() {
        // Arrange: only an unexpected tag is present
        ASN1EncodableVector v = new ASN1EncodableVector();
        v.add(new DERTaggedObject(true, 99, new ASN1Integer(1)));