<objective Payment flows fail in ways generic E2E tests miss: a card field in a cross-origin iframe that silently never reaches, a renewal that won't trigger for a year, a webhook handler that "works" until Stripe retries and fulfills an order twice, an order marked paid on a redirect that the browser forged. This skill makes you test payments the way they actually break — against PSP sandboxes, with the real test cards, the nested 3DS challenge, server-side test clocks, signature-verified webhooks, and idempotent fulfillment. Never a real PAN, never a live key. </objective Quick Route | You…