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Transaction coalescing replaces the original before-image on every update · case 04

Transaction coalescing replaces the original before-image on every update.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Coalesce an ordered transaction of [id,before,after] changes to one net before/after per identity. Keep the first before-image and last after-image, order identities by first touch, suppress equal net states including insert-then-delete, and retain None as absence.

Why this case matters

A bounded deterministic data engine model makes representation and changelog faults reproducible.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
two updates	`[[10, 5, 6]]`	`[[10, 4, 6]]`	Failed

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