In a testMethod, I have following code:

Account_Auditor__c Account_auditor = new Account_Auditor__c(Account__c = a.id, auditor__c = u.id, Audit_Type__c = 'Garbage');

insert Account_auditor;

The intent is to execute the following trigger and give the "Auditor" read rights to the Account .

The testMethod runs fine in developer org, it croaks in the org that it is being installed it - it croaks on the Insert statement with the message:

caused by: System.DmlException: Insert failed. First exception on row 0; first error: INSUFFICIENT_ACCESS_ON_CROSS_REFERENCE_ENTITY, insufficient access rights on cross-reference id

trigger grantAuditorReadAccessToAccount on Account_Auditor__c (after insert) {

Account_Auditor__c[]  Account_auditor_list = trigger.new;

for (Account_Auditor__c Account_auditor: Account_auditor_list) {
AccountShare ashare = new AccountShare();
ashare.AccountAccessLevel = 'Read';
ashare.OpportunityAccessLevel = 'None';
ashare.CaseAccessLevel = 'None';
ashare.AccountId = Account_auditor.Account__c;
ashare.UserorGroupId = Account_auditor.Auditor__c;
Insert ashare;
}
}

I suspect it has something to do with the user rights - I am fetching an active user from the database in the test method (u.id). In the org that I am installing, I have two users, one is system admin, another is a test user I created, so that i could install. I assume I am installing as a