FA-68686 / Toll and parking fee computation / Open access

Merchant parking validations: only the largest flat validation applies · case 01

Merchant parking validations returns a wrong result when only the largest flat validation applies.

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

ROOT CAUSE

Flat validations are treated like percentages and not summed.

THE FAILURE

Flat validations are treated like percentages and not summed.

Unsuccessful approach: Refusing flat validations when a percentage applies is a combinability rule the contract does not have.

Case contract

Input {minutes (single day), validations: [[free_min|pct|flat, value]], hourly, daily_max, max_free_min}. Free minutes from all validations are summed, capped at max_free_min and deducted from the stay before rating. The fee is started hours * hourly capped at daily_max. Only the largest percentage validation applies (discount floored to cents), then all flat validations are subtracted, never below zero.

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):
    free = min(x['max_free_min'], sum(v for k, v in x['validations'] if k == 'free_min'))
    bill = max(0, x['minutes'] - free)
    fee = min(x['daily_max'], -(-bill // 60) * x['hourly'])
    pcts = [v for k, v in x['validations'] if k == 'pct']
    if pcts:
        fee -= fee * max(pcts) // 100
    flat = max([0] + [v for k, v in x['validations'] if k == 'flat'])
    return max(0, fee - flat)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[({'minutes': 552, 'validations': [['flat', 250], ['flat', 500], ['free_min', 15], ['free_min', 15]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 120}, 2250), ({'minutes': 839, 'validations': [['flat', 250], ['free_min', 60], ['flat', 500]], 'hourly': 200, 'daily_max': 1800, 'max_free_min': 120}, 1050), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 977, 'validations': [['flat', 100]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 180}, 2300), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1179, 'validations': [['pct', 10], ['flat', 100]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 180}, 2600), ({'minutes': 226, 'validations': [], 'hourly': 200, 'daily_max': 1800, 'max_free_min': 180}, 800), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550)], [({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 753, 'validations': [['flat', 500], ['free_min', 90], ['free_min', 30], ['flat', 250]], 'hourly': 300, 'daily_max': 1800, 'max_free_min': 60}, 1050), ({'minutes': 780, 'validations': [], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 180}, 2400), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 945, 'validations': [['free_min', 60], ['pct', 50], ['free_min', 30]], 'hourly': 200, 'daily_max': 2400, 'max_free_min': 60}, 1200), ({'minutes': 590, 'validations': [['pct', 10], ['flat', 250], ['flat', 500], ['pct', 50]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 250), ({'minutes': 738, 'validations': [['free_min', 30], ['free_min', 120], ['flat', 100], ['free_min', 120]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 2300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700)], [({'minutes': 761, 'validations': [['free_min', 90], ['flat', 100], ['free_min', 30], ['flat', 500]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 1800), ({'minutes': 745, 'validations': [['flat', 100], ['free_min', 90], ['flat', 250], ['pct', 25]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 60}, 1450), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 1258, 'validations': [], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 3000), ({'minutes': 1149, 'validations': [], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 60}, 2400), ({'minutes': 1112, 'validations': [['flat', 100], ['pct', 10]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 2600), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700)], [({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1372, 'validations': [['pct', 10], ['flat', 250], ['flat', 500], ['free_min', 60]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 1950), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 814, 'validations': [['free_min', 90], ['pct', 50]], 'hourly': 300, 'daily_max': 1800, 'max_free_min': 120}, 900), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 1395, 'validations': [['flat', 250], ['free_min', 90], ['free_min', 90], ['flat', 500]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 1650), ({'minutes': 158, 'validations': [['flat', 250], ['free_min', 90], ['free_min', 30], ['pct', 10]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 0), ({'minutes': 592, 'validations': [['free_min', 15], ['flat', 250]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 180}, 2750)], [({'minutes': 542, 'validations': [['free_min', 30], ['pct', 25], ['flat', 100], ['pct', 10]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 1700), ({'minutes': 1169, 'validations': [['flat', 250], ['flat', 100]], 'hourly': 300, 'daily_max': 3000, 'max_free_min': 180}, 2650), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1262, 'validations': [['flat', 100], ['free_min', 90], ['flat', 250]], 'hourly': 200, 'daily_max': 2400, 'max_free_min': 180}, 2050), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 593, 'validations': [['flat', 100]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 180}, 2300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 1364, 'validations': [['free_min', 60], ['pct', 10]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 2700)]]
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 fixture	Actual	Expected	Outcome
fee oracle 0	`2500`	`2250`	Failed
fee oracle 1	`1300`	`1050`	Failed
fee oracle 2	`700`	`700`	Passed
fee oracle 3	`2300`	`2300`	Passed
fee oracle 4	`300`	`300`	Passed
fee oracle 5	`2600`	`2600`	Passed
fee oracle 6	`800`	`800`	Passed
fee oracle 7	`650`	`550`	Failed

SHA-256 / 9b2b3b9e29fd4315bb99e856a5e3c4cde7ad1a1a5bbfb2493bf06216f4ff80bc

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    free = min(x['max_free_min'], sum(v for k, v in x['validations'] if k == 'free_min'))
    bill = max(0, x['minutes'] - free)
    fee = min(x['daily_max'], -(-bill // 60) * x['hourly'])
    pcts = [v for k, v in x['validations'] if k == 'pct']
    if pcts:
        fee -= fee * max(pcts) // 100
    flat = sum(v for k, v in x['validations'] if k == 'flat') if not pcts else 0
    return max(0, fee - flat)
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[({'minutes': 552, 'validations': [['flat', 250], ['flat', 500], ['free_min', 15], ['free_min', 15]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 120}, 2250), ({'minutes': 839, 'validations': [['flat', 250], ['free_min', 60], ['flat', 500]], 'hourly': 200, 'daily_max': 1800, 'max_free_min': 120}, 1050), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 977, 'validations': [['flat', 100]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 180}, 2300), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1179, 'validations': [['pct', 10], ['flat', 100]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 180}, 2600), ({'minutes': 226, 'validations': [], 'hourly': 200, 'daily_max': 1800, 'max_free_min': 180}, 800), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550)], [({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 753, 'validations': [['flat', 500], ['free_min', 90], ['free_min', 30], ['flat', 250]], 'hourly': 300, 'daily_max': 1800, 'max_free_min': 60}, 1050), ({'minutes': 780, 'validations': [], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 180}, 2400), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 945, 'validations': [['free_min', 60], ['pct', 50], ['free_min', 30]], 'hourly': 200, 'daily_max': 2400, 'max_free_min': 60}, 1200), ({'minutes': 590, 'validations': [['pct', 10], ['flat', 250], ['flat', 500], ['pct', 50]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 250), ({'minutes': 738, 'validations': [['free_min', 30], ['free_min', 120], ['flat', 100], ['free_min', 120]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 2300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700)], [({'minutes': 761, 'validations': [['free_min', 90], ['flat', 100], ['free_min', 30], ['flat', 500]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 1800), ({'minutes': 745, 'validations': [['flat', 100], ['free_min', 90], ['flat', 250], ['pct', 25]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 60}, 1450), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 1258, 'validations': [], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 3000), ({'minutes': 1149, 'validations': [], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 60}, 2400), ({'minutes': 1112, 'validations': [['flat', 100], ['pct', 10]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 2600), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700)], [({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1372, 'validations': [['pct', 10], ['flat', 250], ['flat', 500], ['free_min', 60]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 60}, 1950), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 814, 'validations': [['free_min', 90], ['pct', 50]], 'hourly': 300, 'daily_max': 1800, 'max_free_min': 120}, 900), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 1395, 'validations': [['flat', 250], ['free_min', 90], ['free_min', 90], ['flat', 500]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 1650), ({'minutes': 158, 'validations': [['flat', 250], ['free_min', 90], ['free_min', 30], ['pct', 10]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 0), ({'minutes': 592, 'validations': [['free_min', 15], ['flat', 250]], 'hourly': 350, 'daily_max': 3000, 'max_free_min': 180}, 2750)], [({'minutes': 542, 'validations': [['free_min', 30], ['pct', 25], ['flat', 100], ['pct', 10]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 1700), ({'minutes': 1169, 'validations': [['flat', 250], ['flat', 100]], 'hourly': 300, 'daily_max': 3000, 'max_free_min': 180}, 2650), ({'minutes': 150, 'validations': [['free_min', 60], ['free_min', 60], ['free_min', 60]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 300), ({'minutes': 1262, 'validations': [['flat', 100], ['free_min', 90], ['flat', 250]], 'hourly': 200, 'daily_max': 2400, 'max_free_min': 180}, 2050), ({'minutes': 200, 'validations': [['pct', 25], ['pct', 10], ['flat', 100], ['flat', 250]], 'hourly': 300, 'daily_max': 2400, 'max_free_min': 120}, 550), ({'minutes': 593, 'validations': [['flat', 100]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 180}, 2300), ({'minutes': 95, 'validations': [['free_min', 30]], 'hourly': 350, 'daily_max': 2400, 'max_free_min': 120}, 700), ({'minutes': 1364, 'validations': [['free_min', 60], ['pct', 10]], 'hourly': 200, 'daily_max': 3000, 'max_free_min': 120}, 2700)]]
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 fixture	Actual	Expected	Outcome
fee oracle 0	`2250`	`2250`	Passed
fee oracle 1	`1050`	`1050`	Passed
fee oracle 2	`700`	`700`	Passed
fee oracle 3	`2300`	`2300`	Passed
fee oracle 4	`300`	`300`	Passed
fee oracle 5	`2700`	`2600`	Failed
fee oracle 6	`800`	`800`	Passed
fee oracle 7	`900`	`550`	Failed

SHA-256 / 28560fad134de5fd0ee6f0916a80245c2ff72c299b6a0ac42de385f6df4efe14

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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.

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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 2026-09-29T14:48:04.523411+00:00.

Case digest / e070d8b07581aed0c47af98de6d2138204c6c91342bf43df3db2cc46bae1cc30