byte[] extractedResult = Arrays.copyOfRange(buffer, 5, 21);
        assertEquals(16, extractedResult.length);
    }

    @Test
    void testEngineDigestWithInsufficientBuffer() {
        // Test engineDigest with buffer too small
        HMACT64 hmac = new HMACT64(TEST_KEY);
        hmac.engineUpdate(TEST_DATA, 0, TEST_DATA.length);

        byte[] buffer = new byte[10];