Full Stack Ecommerce Checkout Web App: authored results demonstrate the scoring narrative under fixed reference conditions, not a fresh provider-backed run.
Use integer-cents totals; normalize promos; cap discounts; pre-discount free shipping; enforce stock, double-submit, loading/error, ARIA, and mobile behavior.
Cart table is visible and scannable.
Increment and decrement controls are present.
Order summary includes expected rows.
Promo input and apply action are present.
Checkout reaches a success state.
Avoids floating-point totals and tax drift.
Trims codes and handles case-insensitive matches.
Bad codes produce clear, recoverable feedback.
Discounts cannot push payable total below zero.
Free shipping uses the specified subtotal-before-discount rule.
Unavailable line items prevent checkout.
Repeated clicks cannot create duplicate orders.
Quantities cannot go negative, zero accidentally, or above stock.
Async states are visible and buttons disable while pending.
Core controls work on small screens with labels and keyboard affordances.
Seeded reference: the named domain rules align with every stored checkout check in this scorecard.
Authored fixture conditions only. No provider, sandbox, builder, or Playwright job was freshly executed for this scorecard.