OK, so hit a few walls on this one.

New_Sales_Actual__c is a formula field so I can't set a value.  (It's actually the summary of two opportunity product rollup fields).  But I need the New_Sales_Actual__c to populate and confirm my g1.ClosedBusiness__c

so...

I ended up creating a product and a pricebook in the test to then calculate the New_Sales_Actual__c field in the test opportunities. Was able to get that working (took quite some doing!)

I'm still not there - my Assert is wrong and I can't get the after delete piece figured out.

I know I'm almost there - this is killing me!!  (Although it has been a good learning process).... 

@isTestprivate class testOpportunityRollup {

static testMethod void testOpportunityRollup (){

//Create a Goal

Goal__c g1 = new goal__c(Month__c=Date.valueof('2010-01-01'),ClosedBusiness__c=0);

insert g1;

//Create a new Account:

Account a = new Account(name='Test Account');

insert a;

//Create some Opportunities 

List<Opportunity> opportunities = new List<Opportunity>(); 

Opportunity OP1 = new Opportunity( Name = 'Test Opp 1', AccountId = a.id, CloseDate=Date.valueof('2010-01-01'), StageName='Final Payment Received', Goal__c=g1.id );

Opportunity OP2 = new Opportunity( Name = 'Test Opp 2', AccountId = a.id, CloseDate=Date.valueof('2010-01-01'), StageName='Final Payment Received', Goal__c=g1.id);

Opportunity OP3 = new Opportunity( Name = 'Test Opp 3', AccountId = a.id, CloseDate=Date.valueof('2010-01-01'), StageName='Final Payment Received');

opportunities.add(OP1);

opportunities.add(OP2);

opportunities.add(OP3);

insert opportunities;

// Create Products

Product2 testprod1 = new Product2 (name='test product one1');

testprod1.productcode = 'test pd code1one';

insert testprod1;

Product2 testprod2 = new Product2 (name='test product two2');

testprod2.productcode = 'test pd code2two';

insert testprod2;

// Get Pricebook

Pricebook2 testpb = [select id from Pricebook2 where IsStandard = true];

// Add to pricebook

PricebookEntry testpbe1 = new PricebookEntry ();

testpbe1.pricebook2id = testpb.id; 

testpbe1.product2id = testprod1.id;

testpbe1.IsActive = True;

testpbe1.UnitPrice = 50;

testpbe1.UseStandardPrice = false;

insert testpbe1;

OpportunityLineItem oli1 = new OpportunityLineItem();

oli1.Quantity = 1;

oli1.TotalPrice = 50;

oli1.One_Time_Amount__c = 50;

oli1.Renewable_Amount__c = 0;

oli1.PricebookEntryId = testpbe1.id;

oli1.OpportunityId = OP1.id;

insert oli1;

OpportunityLineItem oli3 = new OpportunityLineItem();

oli3.Quantity = 1;

oli3.TotalPrice = 50;

oli3.One_Time_Amount__c = 50;

oli3.Renewable_Amount__c = 0;

oli3.PricebookEntryId = testpbe1.id;

oli3.OpportunityId = OP2.id;

insert oli3;

System.assert(g1.ClosedBusiness__c <= 100);

//Update Opportunity OP1

Opportunity opp = [select o.Name, o.AccountId, o.CloseDate from Opportunity o where o.Name = 'Test Opp 1' ]; if(opp.Name=='Test Opp 1')

{

opp.Name='Test Opp 1b';

}

update opp;

// After Delete test

}

 Some more Details on the Various Custom Fields:

 New_Sales_Actual__c   (OPPORTUNITY)