Sandbox & testing

All external credentials currently use the una_test_ prefix. The API refuses to start outside sandbox mode. No public request parameter can select production. Provider staging experiments are separately gated and are not production commerce.

Hosted mock checkout supports success, decline, timeout, network failure, authentication-required and authentication-failed scenarios. A lost response may follow a successful capture: reconcile order state and retry the same action key instead of creating a new purchase.

Verify repeated payment commands, concurrent captures, wrong order capability, abandoned checkout, partial refunds, subscription renewals and reserves. Synthetic balances are contractual supplier-compensation fixtures, not withdrawable real funds.