FA-67113 / Railway interlocking logic / Member archive

Two-out-of-three occupancy voting: minimum healthy channels · case 03

A single surviving channel is trusted to declare the section clear.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Three channels report occupancy (True/False) or None when failed. A channel isolated earlier counts as None. With fewer than two healthy channels the vote is occupied. Otherwise the vote is occupied when occupied reports are at least as many as clear ones (ties are occupied). A healthy channel that disagrees with the vote increments its discrepancy count, otherwise (agreeing or None) the count resets; a channel is isolated for good when its count reaches isolate_after. Return all votes and isolated channel indices.

Why this case matters

Interlocking logic decides whether trains may be given authority; a wrong decision at this point either grants unsafe movements or strands traffic.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression: single healthy channel says clear	`{"isolated": [], "votes": [false]}`	`{"isolated": [], "votes": [true]}`	Failed

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