A test key (hlh_test_…) operates on a dedicated sandbox tenant — a completely separate data space. Debtors, cases, payments, and webhook endpoints created with a test key are invisible to live keys, and vice versa.

Test keys are hard-stopped from every live provider: no payment-provider writes, no real SMS or email ever leaves the sandbox.

Webhook events carry a livemode flag: true for live-tenant events, false for sandbox events. Sandbox events are only ever delivered to endpoints registered with a test key.