FA-83872 / Sports scoring and tiebreakers / Member archive

Tiebreak server rotation is off by one point · case 02

The server indicator shows the wrong player after the first point of a tiebreak.

Member previewVariant 2 · 3 implementations · 9 checks per implementation

Case contract

Tiebreak game. points is a string of A/B point winners; target is 7 (standard) or 10 (match tiebreak). The tiebreak ends at the first point where a player has at least target points and a two-point lead; later points are ignored. first_server serves point 0, then serve alternates every two points (point k is served by first_server when ((k + 1) // 2) is even). Return [a, b, winner or None, server of the next point or None when finished, ends_change] where ends_change is true when the tiebreak is unfinished and a positive multiple of 6 points has been played.

Why this case matters

Chair-umpire scoring software must drive the server indicator and change-of-ends prompt during tiebreaks.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
boundary second server pair	`[1, 0, null, "A", false]`	`[1, 0, null, "B", false]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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