byte[] result2 = hmac.engineDigest();

        // Should produce the same result
        assertArrayEquals(result1, result2);
    }

    @Test
    void testDifferentKeysProduceDifferentResults() {
        // Test that different keys produce different results
        byte[] key1 = "key1".getBytes();
        byte[] key2 = "key2".getBytes();

        HMACT64 hmac1 = new HMACT64(key1);