FA-66681 / Airline fare rule evaluation / Open access

Inbound surcharge decided by the outbound date · case 01

A weekend return after a weekday departure is not surcharged, while a weekday return after a weekend departure is.

Verified by executionVariant 1 · 9 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The inbound assessment reads the outbound date.

THE FAILURE

The inbound assessment reads the outbound date.

Unsuccessful approach: Surcharging the inbound only when the outbound was surcharged still ties it to the outbound day.

Case contract

Input {'outbound','inbound' (ISO or None),'weekend_days' ISO digits,'surcharge','rt_rule' EACH|OUTBOUND,'pax'}. Each direction is surcharged by its own departure weekday; with OUTBOUND only the outbound direction is assessed. The per-passenger total is multiplied by pax.

Why this case matters

Day-of-week surcharges are assessed per fare component on its own travel date, and the rule may restrict assessment to the outbound direction.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
N = 1
observations = []
def solve(x):
    wk = x['weekend_days']
    def sur(ds):
        return x['surcharge'] if str(datetime.date.fromisoformat(ds).isoweekday()) in wk else 0
    total = sur(x['outbound'])
    if x['inbound'] is not None and x['rt_rule'] == 'EACH':
        total += sur(x['outbound'])
    return total * x['pax']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['weekday out weekend back', {'outbound': '2027-03-02', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-16', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 1}, 30], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2027-08-29', 'inbound': '2027-09-14', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 5}, 125], ['sampled case 2', {'outbound': '2029-05-04', 'inbound': '2029-05-06', 'weekend_days': '7', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 4}, 40], ['sampled case 3', {'outbound': '2029-02-23', 'inbound': '2029-03-13', 'weekend_days': '57', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 1}, 10]], [['weekday out weekend back', {'outbound': '2027-03-03', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-17', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 2}, 60], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-03', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-10-08', 'inbound': None, 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 2', {'outbound': '2028-10-14', 'inbound': '2028-10-29', 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2027-01-22', 'inbound': '2027-01-27', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 3}, 0]], [['weekday out weekend back', {'outbound': '2027-03-01', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-15', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 3}, 90], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2028-10-14', 'inbound': None, 'weekend_days': '7', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 5}, 0], ['sampled case 2', {'outbound': '2027-03-30', 'inbound': '2027-04-13', 'weekend_days': '7', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2028-09-18', 'inbound': '2028-09-29', 'weekend_days': '67', 'surcharge': 10, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0]], [['weekday out weekend back', {'outbound': '2027-03-02', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-16', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 4}, 120], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-03', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-09-11', 'inbound': '2029-09-13', 'weekend_days': '57', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 4}, 0], ['sampled case 2', {'outbound': '2027-09-08', 'inbound': None, 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2028-08-06', 'inbound': '2028-08-16', 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 2}, 60]], [['weekday out weekend back', {'outbound': '2027-03-03', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-17', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 5}, 150], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-06-29', 'inbound': '2029-07-16', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 2}, 0], ['sampled case 2', {'outbound': '2028-01-20', 'inbound': None, 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 1}, 0], ['sampled case 3', {'outbound': '2028-07-21', 'inbound': None, 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 4}, 100]]]
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
weekday out weekend back	`0`	`50`	Failed
weekend out weekday back	`50`	`25`	Failed
outbound-only rule	`30`	`30`	Passed
one-way weekend	`90`	`90`	Passed
both weekend family	`160`	`160`	Passed
no surcharge	`0`	`0`	Passed
sampled case 1	`250`	`125`	Failed
sampled case 2	`0`	`40`	Failed
sampled case 3	`20`	`10`	Failed

SHA-256 / 97d8e9333862cf2e31d381c853e78e637616b2b6c504b020931d70ff4fb0f1d0

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
N = 1
observations = []
def solve(x):
    wk = x['weekend_days']
    def sur(ds):
        return x['surcharge'] if str(datetime.date.fromisoformat(ds).isoweekday()) in wk else 0
    total = sur(x['outbound'])
    if x['inbound'] is not None and x['rt_rule'] == 'EACH':
        total += sur(x['inbound']) if total else 0
    return total * x['pax']
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['weekday out weekend back', {'outbound': '2027-03-02', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-16', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 1}, 30], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2027-08-29', 'inbound': '2027-09-14', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 5}, 125], ['sampled case 2', {'outbound': '2029-05-04', 'inbound': '2029-05-06', 'weekend_days': '7', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 4}, 40], ['sampled case 3', {'outbound': '2029-02-23', 'inbound': '2029-03-13', 'weekend_days': '57', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 1}, 10]], [['weekday out weekend back', {'outbound': '2027-03-03', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-17', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 2}, 60], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-03', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-10-08', 'inbound': None, 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 2', {'outbound': '2028-10-14', 'inbound': '2028-10-29', 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2027-01-22', 'inbound': '2027-01-27', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 3}, 0]], [['weekday out weekend back', {'outbound': '2027-03-01', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-15', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 3}, 90], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2028-10-14', 'inbound': None, 'weekend_days': '7', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 5}, 0], ['sampled case 2', {'outbound': '2027-03-30', 'inbound': '2027-04-13', 'weekend_days': '7', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2028-09-18', 'inbound': '2028-09-29', 'weekend_days': '67', 'surcharge': 10, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0]], [['weekday out weekend back', {'outbound': '2027-03-02', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-16', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 4}, 120], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-03', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-09-11', 'inbound': '2029-09-13', 'weekend_days': '57', 'surcharge': 10, 'rt_rule': 'EACH', 'pax': 4}, 0], ['sampled case 2', {'outbound': '2027-09-08', 'inbound': None, 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 4}, 0], ['sampled case 3', {'outbound': '2028-08-06', 'inbound': '2028-08-16', 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 2}, 60]], [['weekday out weekend back', {'outbound': '2027-03-03', 'inbound': '2027-03-13', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 2}, 50], ['weekend out weekday back', {'outbound': '2027-03-12', 'inbound': '2027-03-17', 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'EACH', 'pax': 1}, 25], ['outbound-only rule', {'outbound': '2027-03-13', 'inbound': '2027-03-20', 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 5}, 150], ['one-way weekend', {'outbound': '2027-03-14', 'inbound': None, 'weekend_days': '67', 'surcharge': 30, 'rt_rule': 'EACH', 'pax': 3}, 90], ['both weekend family', {'outbound': '2027-03-12', 'inbound': '2027-03-14', 'weekend_days': '567', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 4}, 160], ['no surcharge', {'outbound': '2027-03-02', 'inbound': '2027-03-04', 'weekend_days': '67', 'surcharge': 20, 'rt_rule': 'EACH', 'pax': 2}, 0], ['sampled case 1', {'outbound': '2029-06-29', 'inbound': '2029-07-16', 'weekend_days': '7', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 2}, 0], ['sampled case 2', {'outbound': '2028-01-20', 'inbound': None, 'weekend_days': '57', 'surcharge': 30, 'rt_rule': 'OUTBOUND', 'pax': 1}, 0], ['sampled case 3', {'outbound': '2028-07-21', 'inbound': None, 'weekend_days': '567', 'surcharge': 25, 'rt_rule': 'OUTBOUND', 'pax': 4}, 100]]]
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
weekday out weekend back	`0`	`50`	Failed
weekend out weekday back	`25`	`25`	Passed
outbound-only rule	`30`	`30`	Passed
one-way weekend	`90`	`90`	Passed
both weekend family	`160`	`160`	Passed
no surcharge	`0`	`0`	Passed
sampled case 1	`125`	`125`	Passed
sampled case 2	`0`	`40`	Failed
sampled case 3	`10`	`10`	Passed

SHA-256 / fa1f3d92113f4ea1717b9038fe6a8362221c57612fad2a4f4c7b2c488b09e9ec

HELD IN THE MEMBER ARCHIVE

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

This mechanism has 9 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 stipulated toy fare-rule contract with invented constants; it is not an ATPCO or carrier tariff implementation and makes no claim of industry-standard conformance. 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 2026-09-29T14:47:46.182048+00:00.

Case digest / 50e0ed51267b233f955a6b17c23e916a2302b13c938670e8dfbee4e072ac16df