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

    @Test
    @DisplayName("verifyMIC with null inputs throws NPE")
    void verifyMIC_nullInputs() {
        assertThrows(NullPointerException.class, () -> ctx.verifyMIC(null, new byte[] { 1 }));
        assertThrows(NullPointerException.class, () -> ctx.verifyMIC(new byte[] { 1 }, null));
    }

    @Test