public static Long validateIssuedAt(String claimName, Long claimValue) throws ValidateException {
        if (claimValue != null && claimValue < 0)
            throw new ValidateException(String.format("%s value must be null or non-negative; value given was \"%s\"", claimName, claimValue));

        return claimValue;
    }
@Test
    public void testValidateIssuedAt() {
        Long expected = 1L;
        Long actual = ClaimValidationUtils.validateIssuedAt("iat", expected);
        assertEquals(expected, actual);
    }