public void addALineToAPurchaseOrder()
{
PurchaseOrderFactory s = new PurchaseOrderFactory();
PurchaseOrder res = s.createPurchaseOrder();
int lines = res.Lines.Count;
s.addPurchaseOrderLine(2, "Box", res);
int linesAfter = res.Lines.Count;
Assert.IsTrue(linesAfter == (lines + 1));
}