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 testValidateIssuedAtDisallowsNegatives() {
        assertThrows(ValidateException.class, () -> ClaimValidationUtils.validateIssuedAt("iat", -1L));
    }