Backfill immunity is proved by replay, not by a hand-picked case: a ten-year
Apple Health export (12772 writes) and a 30-day provider re-sync (58 writes)
must both emit zero events, while a fresh sleep night, workout and first
weight of the day emit exactly one each.
The provider-isolation guard walks the worker's static import graph and fails
if any provider client or resolver becomes reachable. It carries two positive
controls, so a broken entry path cannot make it pass against an empty graph.
The integration test covers what unit mocks cannot: the unique index, the
ON CONFLICT DO NOTHING claim, the losing side of ten concurrent claims, the
forward-only marker, ciphertext at rest, the delete cascade, and the
retention window.
Marc-André Bombeck