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FA-66961 / Railway interlocking logic / Open access

Axle counter section supervision: under-count handling · case 01

A section that counted out more axles than in is reported clear.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The negative count is silently clamped to zero without latching the disturbance.

VERIFIED REPAIR

Latch disturbed and zero the count whenever an out-count drives the count below zero.

Unsuccessful approach: Skipping the latch during preparatory reset hides an under-count in the sweep phase.

Case contract

An axle-counter section counts axles in and out. Counting out below zero latches disturbed (count forced to 0). A reset is accepted only when the section is disturbed or the count is non-zero; it zeroes the count and enters preparatory state, which ends only when a sweep train has counted in and the count returns to zero on an out-count. query reports disturbed, prep, occupied (count>0) or clear, in that precedence.

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.

1 / The failure

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    count = 0
    disturbed = False
    prep = False
    swept = False
    out = []
    for ev in x['events']:
        if ev == 'in':
            count += 1
            if prep:
                swept = True
        elif ev == 'out':
            count -= 1
            if count < 0:
                count = 0
            if prep and swept and count == 0:
                prep = False
        elif ev == 'reset':
            if disturbed or count != 0:
                count = 0
                disturbed = False
                prep = True
                swept = False
        elif ev == 'query':
            if disturbed:
                out.append('disturbed')
            elif prep:
                out.append('prep')
            elif count > 0:
                out.append('occupied')
            else:
                out.append('clear')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 3', {'events': ['out', 'reset', 'out', 'in', 'query', 'in', 'query', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('sampled regression 1', {'events': ['out', 'in', 'out', 'query', 'out', 'query', 'in', 'out', 'in', 'out', 'query', 'query', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('control 4', {'events': ['in', 'out', 'query', 'query', 'query']}, ['clear', 'clear', 'clear']), ('sampled regression 7', {'events': ['query', 'out', 'in', 'query', 'out', 'query', 'reset', 'reset', 'in', 'reset', 'query', 'reset', 'query']}, ['clear', 'disturbed', 'disturbed', 'prep', 'prep'])], [('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 10', {'events': ['reset', 'out', 'in', 'query', 'reset', 'in', 'query']}, ['disturbed', 'prep']), ('sampled regression 64', {'events': ['out', 'out', 'in', 'query', 'query', 'reset', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset refused on a clear section', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('sampled regression 12', {'events': ['query', 'out', 'reset', 'out', 'query']}, ['clear', 'disturbed']), ('control 15', {'events': ['out', 'out', 'in', 'reset', 'query', 'query', 'query']}, ['prep', 'prep', 'prep']), ('sampled regression 18', {'events': ['out', 'query', 'query', 'reset', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'prep', 'prep'])], [('regression: sweep train partly through', {'events': ['out', 'reset', 'in', 'in', 'out', 'query', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 21', {'events': ['out', 'in', 'out', 'in', 'query', 'query', 'out', 'query', 'out', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('sampled regression 23', {'events': ['query', 'out', 'query', 'out', 'in', 'in', 'in', 'query', 'out', 'in', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('control 26', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('control 29', {'events': ['out', 'in', 'in', 'out', 'out', 'in', 'reset', 'out', 'reset', 'in', 'query', 'in', 'query']}, ['prep', 'prep'])], [('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 37', {'events': ['reset', 'query', 'out', 'query', 'query', 'out', 'in', 'out', 'in', 'out', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('sampled regression 59', {'events': ['query', 'query', 'in', 'out', 'out', 'reset', 'reset', 'out', 'in', 'query', 'reset', 'query', 'query']}, ['clear', 'clear', 'disturbed', 'prep', 'prep']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('control 34', {'events': ['in', 'out', 'in', 'out', 'in', 'in', 'query']}, ['occupied']), ('control 40', {'events': ['in', 'in', 'query', 'out', 'query']}, ['occupied', 'occupied']), ('sampled regression 43', {'events': ['out', 'in', 'query', 'in', 'query', 'reset', 'reset', 'out', 'reset', 'in', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed'])], [('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 50', {'events': ['out', 'out', 'in', 'query']}, ['disturbed']), ('sampled regression 75', {'events': ['out', 'out', 'out', 'reset', 'out', 'in', 'in', 'query']}, ['disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('sampled regression 45', {'events': ['out', 'query', 'out', 'in', 'query', 'in', 'in', 'in', 'reset', 'in', 'query']}, ['disturbed', 'disturbed', 'prep']), ('sampled regression 48', {'events': ['out', 'query', 'in', 'out', 'reset', 'in', 'query', 'query', 'query', 'query']}, ['disturbed', 'prep', 'prep', 'prep', 'prep']), ('control 51', {'events': ['reset', 'query', 'in', 'out', 'query', 'in', 'in', 'query', 'query', 'query', 'query']}, ['clear', 'clear', 'occupied', 'occupied', 'occupied', 'occupied'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: under-count latches disturbance['clear', 'occupied']['disturbed', 'disturbed']Failed
regression: under-count during preparation['prep']['disturbed']Failed
sampled regression 3['occupied', 'occupied', 'occupied']['disturbed', 'disturbed', 'disturbed']Failed
boundary: reset of a miscounted section['prep', 'prep', 'clear']['prep', 'prep', 'clear']Passed
regression: reset of a disturbed section['clear', 'clear']['prep', 'clear']Failed
sampled regression 1['clear', 'clear', 'clear', 'clear', 'occupied', 'occupied']['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']Failed
control 4['clear', 'clear', 'clear']['clear', 'clear', 'clear']Passed
sampled regression 7['clear', 'occupied', 'clear', 'prep', 'prep']['clear', 'disturbed', 'disturbed', 'prep', 'prep']Failed

SHA-256 / 02f191b707ded85aab52767f10a6886a103a89f0e8126ae2c5b869022ded709a

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    count = 0
    disturbed = False
    prep = False
    swept = False
    out = []
    for ev in x['events']:
        if ev == 'in':
            count += 1
            if prep:
                swept = True
        elif ev == 'out':
            count -= 1
            if count < 0 and not prep:
                disturbed = True
                count = 0
            if prep and swept and count == 0:
                prep = False
        elif ev == 'reset':
            if disturbed or count != 0:
                count = 0
                disturbed = False
                prep = True
                swept = False
        elif ev == 'query':
            if disturbed:
                out.append('disturbed')
            elif prep:
                out.append('prep')
            elif count > 0:
                out.append('occupied')
            else:
                out.append('clear')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 3', {'events': ['out', 'reset', 'out', 'in', 'query', 'in', 'query', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('sampled regression 1', {'events': ['out', 'in', 'out', 'query', 'out', 'query', 'in', 'out', 'in', 'out', 'query', 'query', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('control 4', {'events': ['in', 'out', 'query', 'query', 'query']}, ['clear', 'clear', 'clear']), ('sampled regression 7', {'events': ['query', 'out', 'in', 'query', 'out', 'query', 'reset', 'reset', 'in', 'reset', 'query', 'reset', 'query']}, ['clear', 'disturbed', 'disturbed', 'prep', 'prep'])], [('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 10', {'events': ['reset', 'out', 'in', 'query', 'reset', 'in', 'query']}, ['disturbed', 'prep']), ('sampled regression 64', {'events': ['out', 'out', 'in', 'query', 'query', 'reset', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset refused on a clear section', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('sampled regression 12', {'events': ['query', 'out', 'reset', 'out', 'query']}, ['clear', 'disturbed']), ('control 15', {'events': ['out', 'out', 'in', 'reset', 'query', 'query', 'query']}, ['prep', 'prep', 'prep']), ('sampled regression 18', {'events': ['out', 'query', 'query', 'reset', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'prep', 'prep'])], [('regression: sweep train partly through', {'events': ['out', 'reset', 'in', 'in', 'out', 'query', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 21', {'events': ['out', 'in', 'out', 'in', 'query', 'query', 'out', 'query', 'out', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('sampled regression 23', {'events': ['query', 'out', 'query', 'out', 'in', 'in', 'in', 'query', 'out', 'in', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('control 26', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('control 29', {'events': ['out', 'in', 'in', 'out', 'out', 'in', 'reset', 'out', 'reset', 'in', 'query', 'in', 'query']}, ['prep', 'prep'])], [('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 37', {'events': ['reset', 'query', 'out', 'query', 'query', 'out', 'in', 'out', 'in', 'out', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('sampled regression 59', {'events': ['query', 'query', 'in', 'out', 'out', 'reset', 'reset', 'out', 'in', 'query', 'reset', 'query', 'query']}, ['clear', 'clear', 'disturbed', 'prep', 'prep']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('control 34', {'events': ['in', 'out', 'in', 'out', 'in', 'in', 'query']}, ['occupied']), ('control 40', {'events': ['in', 'in', 'query', 'out', 'query']}, ['occupied', 'occupied']), ('sampled regression 43', {'events': ['out', 'in', 'query', 'in', 'query', 'reset', 'reset', 'out', 'reset', 'in', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed'])], [('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 50', {'events': ['out', 'out', 'in', 'query']}, ['disturbed']), ('sampled regression 75', {'events': ['out', 'out', 'out', 'reset', 'out', 'in', 'in', 'query']}, ['disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('sampled regression 45', {'events': ['out', 'query', 'out', 'in', 'query', 'in', 'in', 'in', 'reset', 'in', 'query']}, ['disturbed', 'disturbed', 'prep']), ('sampled regression 48', {'events': ['out', 'query', 'in', 'out', 'reset', 'in', 'query', 'query', 'query', 'query']}, ['disturbed', 'prep', 'prep', 'prep', 'prep']), ('control 51', {'events': ['reset', 'query', 'in', 'out', 'query', 'in', 'in', 'query', 'query', 'query', 'query']}, ['clear', 'clear', 'occupied', 'occupied', 'occupied', 'occupied'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: under-count latches disturbance['disturbed', 'disturbed']['disturbed', 'disturbed']Passed
regression: under-count during preparation['prep']['disturbed']Failed
sampled regression 3['prep', 'prep', 'clear']['disturbed', 'disturbed', 'disturbed']Failed
boundary: reset of a miscounted section['prep', 'prep', 'clear']['prep', 'prep', 'clear']Passed
regression: reset of a disturbed section['prep', 'clear']['prep', 'clear']Passed
sampled regression 1['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']Passed
control 4['clear', 'clear', 'clear']['clear', 'clear', 'clear']Passed
sampled regression 7['clear', 'disturbed', 'disturbed', 'prep', 'prep']['clear', 'disturbed', 'disturbed', 'prep', 'prep']Passed

SHA-256 / 4751c9db04d12a21cbacde87f0967e66ef878436111a685c5b05b79160f653f1

3 / The verified repair

Exit 0
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(x):
    count = 0
    disturbed = False
    prep = False
    swept = False
    out = []
    for ev in x['events']:
        if ev == 'in':
            count += 1
            if prep:
                swept = True
        elif ev == 'out':
            count -= 1
            if count < 0:
                disturbed = True
                count = 0
            if prep and swept and count == 0:
                prep = False
        elif ev == 'reset':
            if disturbed or count != 0:
                count = 0
                disturbed = False
                prep = True
                swept = False
        elif ev == 'query':
            if disturbed:
                out.append('disturbed')
            elif prep:
                out.append('prep')
            elif count > 0:
                out.append('occupied')
            else:
                out.append('clear')
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 3', {'events': ['out', 'reset', 'out', 'in', 'query', 'in', 'query', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('sampled regression 1', {'events': ['out', 'in', 'out', 'query', 'out', 'query', 'in', 'out', 'in', 'out', 'query', 'query', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('control 4', {'events': ['in', 'out', 'query', 'query', 'query']}, ['clear', 'clear', 'clear']), ('sampled regression 7', {'events': ['query', 'out', 'in', 'query', 'out', 'query', 'reset', 'reset', 'in', 'reset', 'query', 'reset', 'query']}, ['clear', 'disturbed', 'disturbed', 'prep', 'prep'])], [('regression: reset of a disturbed section', {'events': ['out', 'reset', 'query', 'in', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 10', {'events': ['reset', 'out', 'in', 'query', 'reset', 'in', 'query']}, ['disturbed', 'prep']), ('sampled regression 64', {'events': ['out', 'out', 'in', 'query', 'query', 'reset', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed']), ('boundary: reset refused on a clear section', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('sampled regression 12', {'events': ['query', 'out', 'reset', 'out', 'query']}, ['clear', 'disturbed']), ('control 15', {'events': ['out', 'out', 'in', 'reset', 'query', 'query', 'query']}, ['prep', 'prep', 'prep']), ('sampled regression 18', {'events': ['out', 'query', 'query', 'reset', 'in', 'query', 'query']}, ['disturbed', 'disturbed', 'prep', 'prep'])], [('regression: sweep train partly through', {'events': ['out', 'reset', 'in', 'in', 'out', 'query', 'out', 'query']}, ['prep', 'clear']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 21', {'events': ['out', 'in', 'out', 'in', 'query', 'query', 'out', 'query', 'out', 'query', 'query']}, ['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('sampled regression 23', {'events': ['query', 'out', 'query', 'out', 'in', 'in', 'in', 'query', 'out', 'in', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('control 26', {'events': ['reset', 'query', 'in', 'query']}, ['clear', 'occupied']), ('control 29', {'events': ['out', 'in', 'in', 'out', 'out', 'in', 'reset', 'out', 'reset', 'in', 'query', 'in', 'query']}, ['prep', 'prep'])], [('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 37', {'events': ['reset', 'query', 'out', 'query', 'query', 'out', 'in', 'out', 'in', 'out', 'in', 'query']}, ['clear', 'disturbed', 'disturbed', 'disturbed']), ('sampled regression 59', {'events': ['query', 'query', 'in', 'out', 'out', 'reset', 'reset', 'out', 'in', 'query', 'reset', 'query', 'query']}, ['clear', 'clear', 'disturbed', 'prep', 'prep']), ('boundary: normal passage', {'events': ['in', 'in', 'query', 'out', 'out', 'query']}, ['occupied', 'clear']), ('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('control 34', {'events': ['in', 'out', 'in', 'out', 'in', 'in', 'query']}, ['occupied']), ('control 40', {'events': ['in', 'in', 'query', 'out', 'query']}, ['occupied', 'occupied']), ('sampled regression 43', {'events': ['out', 'in', 'query', 'in', 'query', 'reset', 'reset', 'out', 'reset', 'in', 'out', 'out', 'query']}, ['disturbed', 'disturbed', 'disturbed'])], [('regression: under-count latches disturbance', {'events': ['out', 'query', 'in', 'query']}, ['disturbed', 'disturbed']), ('regression: under-count during preparation', {'events': ['in', 'reset', 'out', 'query']}, ['disturbed']), ('sampled regression 50', {'events': ['out', 'out', 'in', 'query']}, ['disturbed']), ('sampled regression 75', {'events': ['out', 'out', 'out', 'reset', 'out', 'in', 'in', 'query']}, ['disturbed']), ('boundary: reset of a miscounted section', {'events': ['in', 'in', 'out', 'reset', 'query', 'in', 'in', 'query', 'out', 'out', 'query']}, ['prep', 'prep', 'clear']), ('sampled regression 45', {'events': ['out', 'query', 'out', 'in', 'query', 'in', 'in', 'in', 'reset', 'in', 'query']}, ['disturbed', 'disturbed', 'prep']), ('sampled regression 48', {'events': ['out', 'query', 'in', 'out', 'reset', 'in', 'query', 'query', 'query', 'query']}, ['disturbed', 'prep', 'prep', 'prep', 'prep']), ('control 51', {'events': ['reset', 'query', 'in', 'out', 'query', 'in', 'in', 'query', 'query', 'query', 'query']}, ['clear', 'clear', 'occupied', 'occupied', 'occupied', 'occupied'])]]
for label, args, expected in fixtures[N-1]:
    check(label, solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)
Boundary fixtureActualExpectedOutcome
regression: under-count latches disturbance['disturbed', 'disturbed']['disturbed', 'disturbed']Passed
regression: under-count during preparation['disturbed']['disturbed']Passed
sampled regression 3['disturbed', 'disturbed', 'disturbed']['disturbed', 'disturbed', 'disturbed']Passed
boundary: reset of a miscounted section['prep', 'prep', 'clear']['prep', 'prep', 'clear']Passed
regression: reset of a disturbed section['prep', 'clear']['prep', 'clear']Passed
sampled regression 1['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']['disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed', 'disturbed']Passed
control 4['clear', 'clear', 'clear']['clear', 'clear', 'clear']Passed
sampled regression 7['clear', 'disturbed', 'disturbed', 'prep', 'prep']['clear', 'disturbed', 'disturbed', 'prep', 'prep']Passed

SHA-256 / 02c008b1dcd416504a412e2ba2f4efbd2efc3ecc8218b5d21df9d64b3c488597

Verification & scope

Stipulated toy interlocking contract for a bounded teaching model; it makes no claim of conformance to any railway signalling standard and omits real safety cases. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:47:48.560887+00:00.

Case digest / 6319fd23294b6a717c80be26618cd07937fdd0c18c0b94a5d0ac9123a36b0550