How to Test Saga Compensation Logic When Distributed Order Steps Fail or Time Out

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A distributed order saga can break when inventory reservation times out after payment is charged, triggering a cancellation flow that may conflict with a late-arriving success response. Without a proper state model, this can result in stock being held indefinitely or a payment being refunded more than once. To guard against this, developers are advised to build an in-memory simulator that injects failure scenarios such as duplicate delivery, late success, refund failure, and process restarts. The simulator enforces three key invariants: a confirmed order has exactly one charge and one reservation, a cancelled order has no net charge and no held stock, and each compensation key triggers at most one external effect. Effects should be made idempotent and reconciliation repeatable, since exactly-once delivery cannot be guaranteed in distributed systems.

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