public static BigInteger decodeQuantity(String value) {
        if (isLongValue(value)) {
            return BigInteger.valueOf(Long.parseLong(value));
        }

        if (!isValidHexQuantity(value)) {
            throw new MessageDecodingException("Value must be in format 0x[0-9a-fA-F]+");
        }

        try {
            return parsePaddedNumberHex(value);
        } catch (NumberFormatException e) {
            throw new MessageDecodingException("Negative ", e);
        }
    }
@Test
    public void testQuantityDecodeMissingPrefix() {

        assertThrows(MessageDecodingException.class, () -> Numeric.decodeQuantity("ff"));
    }