Cover the scenario the server-side load test could not — a guest multi-selecting
10-20 photos at once — by driving the real client path (UploadSheet → /upload →
addToQueue → processQueue → XHR) rather than hitting POST /upload directly.
Two tests assert the properties that keep a guest's photos from being lost:
serial per-device draining (one upload in flight at a time), IndexedDB
persistence (blobs kept until upload, dropped after), every file landing
server-side, and a hard reload mid-burst resuming the rest via loadQueue()
with no photo lost. Injects small per-upload latency via route interception so
the serial drain is observable and the mid-burst reload window is reliable.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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