FAILURE MAP
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FA-60721 / Loyalty points ledgers / Open access

Monthly promotional bonus cap: partial bonus near cap · case 01

A transaction that would exceed the cap gets no bonus at all instead of the remaining allowance.

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

ROOT CAUSE

The bonus is all-or-nothing when it exceeds the remaining cap.

THE FAILURE

The bonus is all-or-nothing when it exceeds the remaining cap.

Unsuccessful approach: Awarding the remainder only when at least half the bonus fits still forfeits valid bonus.

Case contract

Input {cap, txns:[[yyyy-mm, base, bonus, exempt_bonus]]}. Base points are never capped. Regular bonus points are capped per calendar month: each transaction receives min(bonus, cap - bonus already awarded that month). Exempt bonus is always awarded and never uses the cap. Return {awards (base + awarded bonus + exempt per txn), total}.

Why this case matters

Member point balances, statements and the program liability depend on this ledger rule.

1 / The failure

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

N = 1
observations = []
def solve(x):
    used = {}
    out = []
    for m, base, bonus, exempt in x['txns']:
        k = m
        rem = x['cap'] - used.get(k, 0)
        b = bonus if bonus <= rem else 0
        used[k] = used.get(k, 0) + b
        out.append(base + b + exempt)
    return {'awards': out, 'total': sum(out)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2501, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1001, 0]]}, {'awards': [5000, 1001], 'total': 6001}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 901, 0]]}, {'awards': [905, 906], 'total': 1811}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 401, 0]]}, {'awards': [2400, 601], 'total': 3001}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 301, 0]]}, {'awards': [5600, 3301], 'total': 8901}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 251], ['2024-05', 1, 90, 0]]}, {'awards': [252, 91], 'total': 343}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 101, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 501, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2502, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1002, 0]]}, {'awards': [5000, 1002], 'total': 6002}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 902, 0]]}, {'awards': [905, 907], 'total': 1812}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 402, 0]]}, {'awards': [2400, 602], 'total': 3002}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 302, 0]]}, {'awards': [5600, 3302], 'total': 8902}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 252], ['2024-05', 1, 90, 0]]}, {'awards': [253, 91], 'total': 344}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 102, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 502, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2503, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1003, 0]]}, {'awards': [5000, 1003], 'total': 6003}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 903, 0]]}, {'awards': [905, 908], 'total': 1813}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 403, 0]]}, {'awards': [2400, 603], 'total': 3003}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 303, 0]]}, {'awards': [5600, 3303], 'total': 8903}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 253], ['2024-05', 1, 90, 0]]}, {'awards': [254, 91], 'total': 345}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 103, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 503, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2504, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1004, 0]]}, {'awards': [5000, 1004], 'total': 6004}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 904, 0]]}, {'awards': [905, 909], 'total': 1814}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 404, 0]]}, {'awards': [2400, 604], 'total': 3004}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 304, 0]]}, {'awards': [5600, 3304], 'total': 8904}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 254], ['2024-05', 1, 90, 0]]}, {'awards': [255, 91], 'total': 346}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 104, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 504, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2505, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1005, 0]]}, {'awards': [5000, 1005], 'total': 6005}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 905, 0]]}, {'awards': [905, 910], 'total': 1815}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 405, 0]]}, {'awards': [2400, 605], 'total': 3005}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 305, 0]]}, {'awards': [5600, 3305], 'total': 8905}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 255], ['2024-05', 1, 90, 0]]}, {'awards': [256, 91], 'total': 347}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 105, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 505, 0]]}, {'awards': [910, 110], 'total': 1020}]]]
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
cap within month{'awards': [3100, 50, 410], 'total': 3560}{'awards': [3100, 2050, 10], 'total': 5160}Failed
new month resets{'awards': [5000, 1001], 'total': 6001}{'awards': [5000, 1001], 'total': 6001}Passed
same month next year{'awards': [905, 906], 'total': 1811}{'awards': [905, 906], 'total': 1811}Passed
exempt promo{'awards': [2400, 601], 'total': 3001}{'awards': [2400, 601], 'total': 3001}Passed
base never capped{'awards': [5600, 3301], 'total': 8901}{'awards': [5600, 3301], 'total': 8901}Passed
exempt only{'awards': [252, 91], 'total': 343}{'awards': [252, 91], 'total': 343}Passed
many small{'awards': [101, 102, 1, 101], 'total': 305}{'awards': [101, 102, 101, 1], 'total': 305}Failed
little room left{'awards': [910, 10], 'total': 920}{'awards': [910, 110], 'total': 1020}Failed

SHA-256 / cab9acb7a4bdab8b5e6b82ba9c370278914bb308e915e1f0803f43e383fcebf7

2 / The unsuccessful fix

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

N = 1
observations = []
def solve(x):
    used = {}
    out = []
    for m, base, bonus, exempt in x['txns']:
        k = m
        rem = x['cap'] - used.get(k, 0)
        b = min(bonus, rem) if rem >= bonus // 2 else 0
        used[k] = used.get(k, 0) + b
        out.append(base + b + exempt)
    return {'awards': out, 'total': sum(out)}
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2501, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1001, 0]]}, {'awards': [5000, 1001], 'total': 6001}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 901, 0]]}, {'awards': [905, 906], 'total': 1811}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 401, 0]]}, {'awards': [2400, 601], 'total': 3001}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 301, 0]]}, {'awards': [5600, 3301], 'total': 8901}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 251], ['2024-05', 1, 90, 0]]}, {'awards': [252, 91], 'total': 343}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 101, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 501, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2502, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1002, 0]]}, {'awards': [5000, 1002], 'total': 6002}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 902, 0]]}, {'awards': [905, 907], 'total': 1812}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 402, 0]]}, {'awards': [2400, 602], 'total': 3002}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 302, 0]]}, {'awards': [5600, 3302], 'total': 8902}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 252], ['2024-05', 1, 90, 0]]}, {'awards': [253, 91], 'total': 344}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 102, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 502, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2503, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1003, 0]]}, {'awards': [5000, 1003], 'total': 6003}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 903, 0]]}, {'awards': [905, 908], 'total': 1813}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 403, 0]]}, {'awards': [2400, 603], 'total': 3003}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 303, 0]]}, {'awards': [5600, 3303], 'total': 8903}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 253], ['2024-05', 1, 90, 0]]}, {'awards': [254, 91], 'total': 345}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 103, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 503, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2504, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1004, 0]]}, {'awards': [5000, 1004], 'total': 6004}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 904, 0]]}, {'awards': [905, 909], 'total': 1814}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 404, 0]]}, {'awards': [2400, 604], 'total': 3004}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 304, 0]]}, {'awards': [5600, 3304], 'total': 8904}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 254], ['2024-05', 1, 90, 0]]}, {'awards': [255, 91], 'total': 346}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 104, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 504, 0]]}, {'awards': [910, 110], 'total': 1020}]], [['cap within month', {'cap': 5000, 'txns': [['2024-03', 100, 3000, 0], ['2024-03', 50, 2505, 0], ['2024-03', 10, 400, 0]]}, {'awards': [3100, 2050, 10], 'total': 5160}], ['new month resets', {'cap': 5000, 'txns': [['2024-03', 0, 5000, 0], ['2024-04', 0, 1005, 0]]}, {'awards': [5000, 1005], 'total': 6005}], ['same month next year', {'cap': 1000, 'txns': [['2023-07', 5, 900, 0], ['2024-07', 5, 905, 0]]}, {'awards': [905, 910], 'total': 1815}], ['exempt promo', {'cap': 2000, 'txns': [['2024-01', 200, 1500, 700], ['2024-01', 200, 405, 0]]}, {'awards': [2400, 605], 'total': 3005}], ['base never capped', {'cap': 1000, 'txns': [['2024-02', 5000, 600, 0], ['2024-02', 3000, 305, 0]]}, {'awards': [5600, 3305], 'total': 8905}], ['exempt only', {'cap': 100, 'txns': [['2024-05', 1, 0, 255], ['2024-05', 1, 90, 0]]}, {'awards': [256, 91], 'total': 347}], ['many small', {'cap': 300, 'txns': [['2024-06', 1, 100, 0], ['2024-06', 1, 100, 1], ['2024-06', 1, 105, 0], ['2024-06', 1, 100, 0]]}, {'awards': [101, 102, 101, 1], 'total': 305}], ['little room left', {'cap': 1000, 'txns': [['2024-08', 10, 900, 0], ['2024-08', 10, 505, 0]]}, {'awards': [910, 110], 'total': 1020}]]]
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
cap within month{'awards': [3100, 2050, 10], 'total': 5160}{'awards': [3100, 2050, 10], 'total': 5160}Passed
new month resets{'awards': [5000, 1001], 'total': 6001}{'awards': [5000, 1001], 'total': 6001}Passed
same month next year{'awards': [905, 906], 'total': 1811}{'awards': [905, 906], 'total': 1811}Passed
exempt promo{'awards': [2400, 601], 'total': 3001}{'awards': [2400, 601], 'total': 3001}Passed
base never capped{'awards': [5600, 3301], 'total': 8901}{'awards': [5600, 3301], 'total': 8901}Passed
exempt only{'awards': [252, 91], 'total': 343}{'awards': [252, 91], 'total': 343}Passed
many small{'awards': [101, 102, 101, 1], 'total': 305}{'awards': [101, 102, 101, 1], 'total': 305}Passed
little room left{'awards': [910, 10], 'total': 920}{'awards': [910, 110], 'total': 1020}Failed

SHA-256 / 9cc3533dcd9495ba2aab38d087f781887f7bff446a7ed3c1eaf9a0ef327d992e

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

Stipulated bounded loyalty-program model with explicit toy rules; not any real program terms. 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 2026-09-29T14:46:48.296174+00:00.

Case digest / 071c1a06382549a07d4e94cc9d6d624e6e614278a37068e2d322bfff8a8a3882