Pretty new to writing test classes, was looking for help for this trigger:

trigger SumPositions on Investor__c (before insert, before update, before delete) {
    for (Investor__c record : Trigger.new) {
        record.Sum_of_Positions__c = null;
    }
    for(AggregateResult result: [SELECT SEI_Investor_Id__c, SUM(Position__c.Balance__c)
                                 FROM Position__c WHERE SEI_Investor_Id__c
                                 IN :Trigger.newMap.keyset() GROUP BY SEI_Investor_Id__c]) {
         Trigger.newMap.get(result.get('SEI_Investor_Id__c')).Sum_of_Positions__c = (Decimal)result.get('expr0');
     }
 }

Hi ,

I need to get the submitted record id to pass through my custom redirect link in form assembly. Could you please assist?.

In my case,
I have submited the form record in custom object, here I need to get the  record id of my submitted record and pass this id to my customized redirect url.