byte[] buffer = new byte[10];
        // Should throw exception when buffer is too small
        assertThrows(IllegalStateException.class, () -> hmac.engineDigest(buffer, 0, 10));
    }

    @Test
    void testClone() {
        // Test clone() method
        HMACT64 originalHmac = new HMACT64(TEST_KEY);
        originalHmac.engineUpdate(TEST_DATA, 0, TEST_DATA.length / 2);

            HMACT64 hmac = new HMACT64(TEST_KEY);
            assertThrows(IllegalStateException.class, () -> hmac.engineDigest(new byte[10], 0, 10));
        }
    }

    @Test
    void testClone() throws NoSuchAlgorithmException, CloneNotSupportedException {
        // Test clone() method
        try (MockedStatic<Crypto> mockedCrypto = mockStatic(Crypto.class)) {