Software that real businesses run on.

207of 396 items

showed stock but could not be sold.

Opening stock had been typed in without purchase records, so the costing engine had nothing to sell from. I traced it and made the cause visible to the owner.

Every sale consumes stock batch by batch.

FIFO costing at the cashier, so the cost of every item sold is the price it was actually bought at.

// simplified
foreach (oldestBatchesFirst($item) as $batch) {
    $take  = min($batch->remaining, $qty);
    $cost += $take * $batch->unitCost;
}

Profit reports that stopped flattering.

Fixed two bugs that overstated margins, so the profit report matches the money.

Receivables with due dates.

Credit sales and partial payments in one list, with overdue invoices flagged.

208automated tests

Shipped in phases, live in production.

Cashiers lost access to admin-only actions, and every change lands behind a test.