assertTrue(ex.getMessage().contains("Bad textual SID format"));
        }

        @Test
        @DisplayName("Textual constructor null throws NullPointerException")
        void testTextualConstructorNull() {
            assertThrows(NullPointerException.class, () -> new SID((String) null));
        }

        @Test
        @DisplayName("Binary constructor happy path and round-trip via toByteArray")