Standing in for the real thingintermediate
When a function returns nothing and just calls something else, you test it by passing in a fake that writes down what it was asked to do — no network, no cost, no message sent to a real customer.
The function returns nothing. Observe what it did instead.
Your suite passes a correct alertLowStock and fails five that each get it subtly wrong.
Published in full, before you start — every point is one of these and there is nothing else. Each one runs your code; it is not a search for keywords.
When a function returns nothing and just calls something else, you test it by passing in a fake that writes down what it was asked to do — no network, no cost, no message sent to a real customer.