Group group = is.getGroup("LoginIfcGroup");
assertNotNull(group);
Field userNameField = group.get("Username");
ParserService ps = (ParserService) this.resolve( ParserService.class.getName() );
ValueParser pp = ps.getParser(DefaultParameterParser.class);
pp.setString(userNameField.getKey(), "Joe");
userNameField.init(pp);
userNameField.validate();