Attached is the current inventory item list we have recorded. 

I understand the concept of creating the Item, Product Testing, and using Product Testing as the Income Account. I do not understand how the quantities would move from the Inventory Part to Product Testing via the invoice. When invoicing, if the item code is one from Product Testing, then how would it pull from the regular, Item Inventory Part. For example, if I have WICKS, CD-16, Inventory Part, Merchandise Sales. This is where I recorded the inventory from the invoice. You mentioned to create item  for product testing, for example, WICKS (Product Testing), CD-16, Inventory Part, Product Testing, how do we move the quantities from one to the other using the invoice method? Thanks