A tax invoice in Cameroon is a legal document, not a receipt template. It has to be numbered in an unbroken sequence, carry the statutory TVA breakdown, and remain reproducible years later — even after the product it references has been edited or deleted.
What I did about it
Invoices snapshot their line items at issue time rather than joining live to the catalogue, so editing a product never rewrites history.
Webhook idempotency is tested, not assumed — a replayed payment callback cannot issue a second invoice against the same order.
Seven separate service units — API, worker, scheduler, backup, low-stock job and more — so a slow report cannot block checkout.
What I rejected, and why
Only 22 backend tests. The money paths are covered; the catalogue surface leans on manual QA. Stated plainly rather than papered over.
Twenty-two backend tests for a system issuing statutory TVA invoices. The money paths and webhook idempotency are covered; the catalogue and loyalty surfaces lean on manual QA, which does not scale past one maintainer.