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FA-68471 / Toll and parking fee computation / Open access

Street meter time purchase: purchased time runs past enforcement end · case 01

Street meter time purchase returns a wrong result when purchased time runs past enforcement end.

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

ROOT CAUSE

Time is sold after enforcement ends, when parking is free.

THE FAILURE

Time is sold after enforcement ends, when parking is free.

Unsuccessful approach: Clipping at midnight still sells the free evening hours.

Case contract

Input {now, expiry (or null), paid_cents, rate_per_hour, max_minutes, enf_start, enf_end, increment}. Only whole increments are credited. At or after enforcement end nothing is sold: [null, 0]. Paid time starts at the later of now, enforcement start and any unexpired expiry; it ends at the earliest of start + purchased minutes (floor), max(now, enf_start) + max_minutes, and enf_end. Accepted cents = min(credited, ceil(used minutes * rate/60)). Return [new expiry, accepted cents].

Why this case matters

Fee engines bill customers in integer cents; a wrong boundary, rounding stage or cap scope silently over- or under-charges.

1 / The failure

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

N = 1
observations = []
def solve(x):
    inc = x['increment']
    c = x['paid_cents'] - x['paid_cents'] % inc
    now = x['now']
    if now >= x['enf_end']:
        return [None, 0]
    base = max(now, x['enf_start'])
    start = base if x['expiry'] is None else max(base, x['expiry'])
    mins = c * 60 // x['rate_per_hour']
    end = min(start + mins, base + x['max_minutes'])
    used = max(0, end - start)
    cost = min(c, -(-used * x['rate_per_hour'] // 60))
    return [max(end, start), cost]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[({'now': 1044, 'expiry': None, 'paid_cents': 169, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 60]), ({'now': 600, 'expiry': 650, 'paid_cents': 400, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [720, 234]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1023, 'expiry': 1036, 'paid_cents': 13, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1036, 0]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 480, 'expiry': None, 'paid_cents': 6, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [480, 0]), ({'now': 1031, 'expiry': None, 'paid_cents': 459, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 205]), ({'now': 1046, 'expiry': 1039, 'paid_cents': 578, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 57])], [({'now': 1080, 'expiry': 1051, 'paid_cents': 305, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 943, 'expiry': 889, 'paid_cents': 449, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1045, 425]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1080, 'expiry': 1060, 'paid_cents': 69, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 946, 'expiry': 902, 'paid_cents': 565, 'rate_per_hour': 100, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 224]), ({'now': 1023, 'expiry': 1102, 'paid_cents': 159, 'rate_per_hour': 150, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1102, 0])], [({'now': 878, 'expiry': 862, 'paid_cents': 455, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [998, 200]), ({'now': 991, 'expiry': 997, 'paid_cents': 386, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 277]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 600, 'expiry': 650, 'paid_cents': 400, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [720, 234]), ({'now': 1080, 'expiry': 1158, 'paid_cents': 156, 'rate_per_hour': 150, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 331, 'expiry': 299, 'paid_cents': 450, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [600, 300]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1055, 'expiry': 1058, 'paid_cents': 559, 'rate_per_hour': 150, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 55])], [({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1080, 'expiry': 1151, 'paid_cents': 314, 'rate_per_hour': 200, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 480, 'expiry': 478, 'paid_cents': 452, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 100]), ({'now': 972, 'expiry': None, 'paid_cents': 526, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 270]), ({'now': 1018, 'expiry': 1010, 'paid_cents': 189, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 104]), ({'now': 1080, 'expiry': None, 'paid_cents': 266, 'rate_per_hour': 200, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0])], [({'now': 1415, 'expiry': 1420, 'paid_cents': 119, 'rate_per_hour': 200, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1080, 'expiry': 1140, 'paid_cents': 5, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1080, 'expiry': 1030, 'paid_cents': 119, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1075, 'expiry': 1017, 'paid_cents': 282, 'rate_per_hour': 250, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 21]), ({'now': 1011, 'expiry': 1080, 'paid_cents': 532, 'rate_per_hour': 200, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 0])]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check('fee oracle' + ' %d' % i, 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
fee oracle 0[1104, 100][1080, 60]Failed
fee oracle 1[720, 234][720, 234]Passed
fee oracle 2[None, 0][None, 0]Passed
fee oracle 3[1036, 0][1036, 0]Passed
fee oracle 4[540, 200][540, 200]Passed
fee oracle 5[480, 0][480, 0]Passed
fee oracle 6[1139, 450][1080, 205]Failed
fee oracle 7[1106, 100][1080, 57]Failed

SHA-256 / 6b9ab66ef8c5a8a559b91b9b3a7ad01c1beddd27ea13f0f44db22a14c04a0cbd

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    inc = x['increment']
    c = x['paid_cents'] - x['paid_cents'] % inc
    now = x['now']
    if now >= x['enf_end']:
        return [None, 0]
    base = max(now, x['enf_start'])
    start = base if x['expiry'] is None else max(base, x['expiry'])
    mins = c * 60 // x['rate_per_hour']
    end = min(start + mins, base + x['max_minutes'], 1440)
    used = max(0, end - start)
    cost = min(c, -(-used * x['rate_per_hour'] // 60))
    return [max(end, start), cost]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[({'now': 1044, 'expiry': None, 'paid_cents': 169, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 60]), ({'now': 600, 'expiry': 650, 'paid_cents': 400, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [720, 234]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1023, 'expiry': 1036, 'paid_cents': 13, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1036, 0]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 480, 'expiry': None, 'paid_cents': 6, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [480, 0]), ({'now': 1031, 'expiry': None, 'paid_cents': 459, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 205]), ({'now': 1046, 'expiry': 1039, 'paid_cents': 578, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 57])], [({'now': 1080, 'expiry': 1051, 'paid_cents': 305, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 943, 'expiry': 889, 'paid_cents': 449, 'rate_per_hour': 250, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1045, 425]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1080, 'expiry': 1060, 'paid_cents': 69, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 946, 'expiry': 902, 'paid_cents': 565, 'rate_per_hour': 100, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 224]), ({'now': 1023, 'expiry': 1102, 'paid_cents': 159, 'rate_per_hour': 150, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1102, 0])], [({'now': 878, 'expiry': 862, 'paid_cents': 455, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [998, 200]), ({'now': 991, 'expiry': 997, 'paid_cents': 386, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 277]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 600, 'expiry': 650, 'paid_cents': 400, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [720, 234]), ({'now': 1080, 'expiry': 1158, 'paid_cents': 156, 'rate_per_hour': 150, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 331, 'expiry': 299, 'paid_cents': 450, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [600, 300]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1055, 'expiry': 1058, 'paid_cents': 559, 'rate_per_hour': 150, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 55])], [({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1080, 'expiry': 1151, 'paid_cents': 314, 'rate_per_hour': 200, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 480, 'expiry': 478, 'paid_cents': 452, 'rate_per_hour': 100, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 100]), ({'now': 972, 'expiry': None, 'paid_cents': 526, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 270]), ({'now': 1018, 'expiry': 1010, 'paid_cents': 189, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 104]), ({'now': 1080, 'expiry': None, 'paid_cents': 266, 'rate_per_hour': 200, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0])], [({'now': 1415, 'expiry': 1420, 'paid_cents': 119, 'rate_per_hour': 200, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 1080, 'expiry': 1140, 'paid_cents': 5, 'rate_per_hour': 100, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [None, 0]), ({'now': 420, 'expiry': None, 'paid_cents': 200, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [540, 200]), ({'now': 1040, 'expiry': None, 'paid_cents': 333, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [1080, 100]), ({'now': 1080, 'expiry': 1100, 'paid_cents': 100, 'rate_per_hour': 200, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1080, 'expiry': 1030, 'paid_cents': 119, 'rate_per_hour': 150, 'max_minutes': 120, 'enf_start': 480, 'enf_end': 1080, 'increment': 25}, [None, 0]), ({'now': 1075, 'expiry': 1017, 'paid_cents': 282, 'rate_per_hour': 250, 'max_minutes': 60, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 21]), ({'now': 1011, 'expiry': 1080, 'paid_cents': 532, 'rate_per_hour': 200, 'max_minutes': 240, 'enf_start': 480, 'enf_end': 1080, 'increment': 5}, [1080, 0])]]
for i, (args, expected) in enumerate(fixtures[N-1]):
    check('fee oracle' + ' %d' % i, 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
fee oracle 0[1104, 100][1080, 60]Failed
fee oracle 1[720, 234][720, 234]Passed
fee oracle 2[None, 0][None, 0]Passed
fee oracle 3[1036, 0][1036, 0]Passed
fee oracle 4[540, 200][540, 200]Passed
fee oracle 5[480, 0][480, 0]Passed
fee oracle 6[1139, 450][1080, 205]Failed
fee oracle 7[1106, 100][1080, 57]Failed

SHA-256 / ee3838f08b4c994e7c28b025c4235ad31ee93c9fdee7f7e7776b4699fc26ab6d

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

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Verification & scope

A deterministic, bounded toy model with a stipulated contract; it makes no claim of conformance to any agency manual or standard. 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 2026-09-29T14:48:02.525803+00:00.

Case digest / f87a3033a374e517857c845ab176fc451df62d2d242803030f3283b711e4f223