assertTrue(ex.getMessage().contains("Failed to calculate MIC"));
    }

    @Test
    @DisplayName("calculateMIC with null data throws NPE")
    void calculateMIC_nullData() {
        assertThrows(NullPointerException.class, () -> ctx.calculateMIC(null));
    }

    @Test
    @DisplayName("verifyMIC delegates to GSS and succeeds")
    void verifyMIC_success() throws Exception {