What would you test before closing this cart-total defect?

A fictional cart contains item A at $12.00 with quantity 2 and item B at $8.00 with quantity 1. There are no discounts, taxes, shipping charges or inventory constraints in this fixture. The subtotal is $32.00. The reported defect is that deleting item A removes its row but leaves the subtotal at $32.00. A candidate fix changes the shared cart-total recalculation used by deletion and quantity updates. The product contract says deletion removes the whole selected line, the updated cart persists after reload, an empty cart has a $0.00 subtotal, and checkout is disabled when empty.