FA-44650 / Data systems / Member archive

Distinct mutates its before-image while applying changes · case 05

Distinct mutates its before-image while applying changes.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Maintain bag counts from consolidated signed changes and emit only membership crossings. Old and delta entries are [value,count]; counts after each batch are nonnegative. Output sorted [value,+1/-1] for zero-to-positive or positive-to-zero transitions.

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
new singleton	`[]`	`[[5, 1]]`	Failed

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