| Provider and method | Your provider has enabled your live merchant account, currency and payment method. Test credentials and a successful sandbox payment cover only the sandbox connection. |
| Checkout | On a test order, follow the buyer redirect through success, decline and abandonment. Check what the order shows if the buyer closes the browser before returning. |
| Orders | A retry with the original idempotency key and body returns the same attempt. A delayed result leaves the order pending. Fulfil only once after matching the successful transaction to the expected order. |
| Webhooks | Verify signatures on the raw body. Send a duplicate event through your handler and check that it cannot fulfil the order twice. Test the live endpoint and its signing secret separately from test mode. |
| Refunds | For each provider offering refunds, exercise a supported refund in the sandbox. Record the refund ID and follow it to its final status. |
| Support | Confirm who can see the transaction, look up the provider reference and reconcile an order if a webhook is late. |
