Delete OrderItem Error

Question

When I try to delete an OrderItem from an Order, I am getting a DML Mixed Exception. However, I am not updating any other object.

Am I missing something?

@istest
private class TestDeleteOrderItemEntry {

@future
static void del(Id oli) {
    database.delete(oli);
    system.assertEquals(0, [SELECT Id FROM OrderItem].size());
}

static testMethod void testDelete(){

    Test.startTest();

    Account a = new Account(Name='TestAccount');
    insert a;

    Contract c = new Contract(AccountId=a.Id, Name='TestContract',StartDate=system.today().toStartOfMonth(),ContractTerm=30,Status='Draft');
    insert c;

    c.Status = 'Activated';
    update c;

    Pricebook2 pb = new Pricebook2(Name='TestPriceBook');
    insert pb;

    Product2 prod = new Product2(Name = 'TestProduct');
    insert prod;

    Order o = new Order(AccountId=a.Id,ContractId=c.Id,EndDate=system.now().addDays(1).date());
    o.EffectiveDate  = system.today();
    o.Status = 'Draft';
    o.Pricebook2Id = pb.Id;
    o.EndDate = system.today();
    insert o;

    PricebookEntry standardPrice = new PricebookEntry(
    Pricebook2Id = Test.getStandardPricebookId(), Product2Id = prod.Id,
    UnitPrice = 10000, IsActive = true);
    insert standardPrice;

    PricebookEntry priceEntry = new PricebookEntry(
    Pricebook2Id = pb.Id, Product2Id = prod.Id,
    UnitPrice = 10000, IsActive = true, UseStandardPrice=true);        
    insert priceEntry;

    OrderItem item = new OrderItem(OrderId=o.Id, Quantity=1, UnitPrice=3, PriceBookEntryId=priceEntry.Id);
    insert item;

    del(item.Id);

    Test.stopTest();
}

}

Error:

15:10:59:712 FATAL_ERROR System.DmlException: Delete failed. First exception on row 0 with id 8027A0000008qQYQAY; 
            first error: MIXED_DML_OPERATION, DML operation on setup object is not permitted 
            after you have updated a non-setup object (or vice versa):
            CustomFieldDefinition, original object: OrderItem: []

Thanks,

Answer 1

The cause of the issue was a custom roll-up field on the Contract. Go Figure. I was SUMing the total order amounts across all orders for a certain contract.

To fix this issue, I created a custom formula field "TotalAmount2" on an Order. Then created a roll-up field across that custom field on the Contract.

Hope this helps someone else.