This is a performance test adding 100 orders, and one lineitem. In
teardown, when deleting the first order, the lineitem can’t be deleted
as it is referenced by 99 other orders. (One order has many lineitems).
So test_save_bulk_orders fails.
My suggestion is to change teardown:
def teardown
LineItem.delete_all
Order.delete_all
end
or adding one lineitem per order in the fixture.