FA-85711 / Ride-hailing fare and surge pricing / Open access

Card payments rounded to the cash step · case 01

Swiss card payments are rounded to 5 centimes.

Verified by executionVariant 1 · 7 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Cash rounding runs for every payment method.

VERIFIED REPAIR

Round only cash payments.

Unsuccessful approach: Excluding only cards still rounds wallet payments.

Case contract

Convert a fare to the payment currency with the directed rate fx[FROM+TO] = [num, den] (half up), then, for cash payments only, round half up to the payment currency cash step (CHF 5 centimes, SEK 100 ore, others 1). Card and wallet payments are not cash-rounded. Return the amount in minor units of the payment currency.

Why this case matters

Ride-hailing prices are computed per trip at scale; ordering, unit and boundary slips become systematic over- or under-charging.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(fare_cents, fare_ccy, pay_ccy, method, fx, cash_step):
    amt = fare_cents
    if pay_ccy != fare_ccy:
        num, den = fx[fare_ccy + pay_ccy]
        amt = (amt * num * 2 + den) // (2 * den)
    if True:
        step = cash_step.get(pay_ccy, 1)
        amt = (amt * 2 + step) // (2 * step) * step
    return amt
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: cash-only rounding',
   [4478, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4478),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 2',
   [1999, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1880),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [1234, 'CHF', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1283)],
 [('regression: cash-only rounding',
   [1999, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [2928, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2928),
  ('second regression',
   [1003, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('normal control 1',
   [1234, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [1003, 'SEK', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 4',
   [517, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   500)],
 [('regression: cash-only rounding',
   [1003, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1234),
  ('normal control 1',
   [1796, 'SEK', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   162),
  ('normal control 2',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 3',
   [2502, 'CHF', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2500),
  ('normal control 4',
   [1234, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   111)],
 [('regression: cash-only rounding',
   [2502, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('partial repair probe: cash-only rounding',
   [1003, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003),
  ('second regression',
   [2502, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2352),
  ('normal control 1',
   [1234, 'EUR', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [4790, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4505)],
 [('regression: cash-only rounding',
   [1999, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1999, 'CHF', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2079),
  ('normal control 2',
   [1234, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 3',
   [1234, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 4',
   [1003, 'EUR', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003)]]
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 fixture	Actual	Expected	Outcome
regression: cash-only rounding	`4480`	`4478`	Failed
partial repair probe: cash-only rounding	`2000`	`1999`	Failed
second regression	`14200`	`14154`	Failed
normal control 1	`90`	`90`	Passed
normal control 2	`1880`	`1880`	Passed
normal control 3	`2350`	`2350`	Passed
normal control 4	`1283`	`1283`	Passed

SHA-256 / 2fbf824623ed896a12ab19c77a840a444ff0f15ca35d0a33c16d755432d00990

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(fare_cents, fare_ccy, pay_ccy, method, fx, cash_step):
    amt = fare_cents
    if pay_ccy != fare_ccy:
        num, den = fx[fare_ccy + pay_ccy]
        amt = (amt * num * 2 + den) // (2 * den)
    if method != 'card':
        step = cash_step.get(pay_ccy, 1)
        amt = (amt * 2 + step) // (2 * step) * step
    return amt
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: cash-only rounding',
   [4478, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4478),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 2',
   [1999, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1880),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [1234, 'CHF', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1283)],
 [('regression: cash-only rounding',
   [1999, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [2928, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2928),
  ('second regression',
   [1003, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('normal control 1',
   [1234, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [1003, 'SEK', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 4',
   [517, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   500)],
 [('regression: cash-only rounding',
   [1003, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1234),
  ('normal control 1',
   [1796, 'SEK', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   162),
  ('normal control 2',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 3',
   [2502, 'CHF', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2500),
  ('normal control 4',
   [1234, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   111)],
 [('regression: cash-only rounding',
   [2502, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('partial repair probe: cash-only rounding',
   [1003, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003),
  ('second regression',
   [2502, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2352),
  ('normal control 1',
   [1234, 'EUR', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [4790, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4505)],
 [('regression: cash-only rounding',
   [1999, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1999, 'CHF', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2079),
  ('normal control 2',
   [1234, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 3',
   [1234, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 4',
   [1003, 'EUR', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003)]]
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 fixture	Actual	Expected	Outcome
regression: cash-only rounding	`4478`	`4478`	Passed
partial repair probe: cash-only rounding	`2000`	`1999`	Failed
second regression	`14154`	`14154`	Passed
normal control 1	`90`	`90`	Passed
normal control 2	`1880`	`1880`	Passed
normal control 3	`2350`	`2350`	Passed
normal control 4	`1283`	`1283`	Passed

SHA-256 / 2b9fc175b1ed36950c5d475095f6a7dbd6f97191e805843a0abd2fb65ed5fd9f

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(fare_cents, fare_ccy, pay_ccy, method, fx, cash_step):
    amt = fare_cents
    if pay_ccy != fare_ccy:
        num, den = fx[fare_ccy + pay_ccy]
        amt = (amt * num * 2 + den) // (2 * den)
    if method == 'cash':
        step = cash_step.get(pay_ccy, 1)
        amt = (amt * 2 + step) // (2 * step) * step
    return amt
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression: cash-only rounding',
   [4478, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4478),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 2',
   [1999, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1880),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [1234, 'CHF', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1283)],
 [('regression: cash-only rounding',
   [1999, 'CHF', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [2928, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2928),
  ('second regression',
   [1003, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('normal control 1',
   [1234, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [1003, 'SEK', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 4',
   [517, 'SEK', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   500)],
 [('regression: cash-only rounding',
   [1003, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   943),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1234),
  ('normal control 1',
   [1796, 'SEK', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   162),
  ('normal control 2',
   [1003, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   90),
  ('normal control 3',
   [2502, 'CHF', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2500),
  ('normal control 4',
   [1234, 'SEK', 'EUR', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   111)],
 [('regression: cash-only rounding',
   [2502, 'SEK', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('partial repair probe: cash-only rounding',
   [1003, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003),
  ('second regression',
   [2502, 'EUR', 'CHF', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2352),
  ('normal control 1',
   [1234, 'EUR', 'SEK', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14200),
  ('normal control 2',
   [2502, 'EUR', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2502),
  ('normal control 3',
   [2502, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2350),
  ('normal control 4',
   [4790, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   4505)],
 [('regression: cash-only rounding',
   [1999, 'SEK', 'SEK', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('partial repair probe: cash-only rounding',
   [1999, 'CHF', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1999),
  ('second regression',
   [1234, 'EUR', 'SEK', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   14154),
  ('normal control 1',
   [1999, 'CHF', 'EUR', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   2079),
  ('normal control 2',
   [1234, 'EUR', 'CHF', 'wallet',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 3',
   [1234, 'EUR', 'CHF', 'cash',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1160),
  ('normal control 4',
   [1003, 'EUR', 'EUR', 'card',
    {'CHFEUR': [104, 100], 'EURCHF': [94, 100], 'EURSEK': [1147, 100], 'SEKEUR': [9, 100]},
    {'CHF': 5, 'SEK': 100}],
   1003)]]
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 fixture	Actual	Expected	Outcome
regression: cash-only rounding	`4478`	`4478`	Passed
partial repair probe: cash-only rounding	`1999`	`1999`	Passed
second regression	`14154`	`14154`	Passed
normal control 1	`90`	`90`	Passed
normal control 2	`1880`	`1880`	Passed
normal control 3	`2350`	`2350`	Passed
normal control 4	`1283`	`1283`	Passed

SHA-256 / 86bf9dfcc4cd1722e808a17de9cc4dc3554500945fb23a43a426d17f228358bc

Verification & scope

A deterministic toy pricing contract stipulated for this example; it does not reproduce the pricing of any real ride-hailing operator or regulator. 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 2026-09-29T14:50:42.920413+00:00.

Case digest / 0f99afd37cbc90bcc90678bf362dddd502d27ccf7e886bb52796c3fb761e997c