ok, I have to be doing something stupid, but I can't see it.

var empRecord = record.load({type: record.Type.EMPLOYEE, id: 123, isDynamic: true});
empRecord.setValue({fieldId: 'jobdescription', value: 'whatever'});
var saved_id = empRecord.save();
log.debug("Saved as expected: "+saved_id);

But that value remains the old value.

setValue

and

setText

both just do nothing silently. Can anyone point out where I'm being stupid, please? (lots of error handling is left out of that contrived example)