FA-58536 / Loan amortization schedules / Open access
Late fee after grace period: fee base · case 01
Late but complete payments are charged only the minimum fee.
ROOT CAUSE
The fee is computed on the shortfall instead of the scheduled payment.
VERIFIED REPAIR
Compute the fee on the scheduled payment due.
Unsuccessful approach: Using the amount paid charges nothing for unpaid installments.
Case contract
x = {'due_day', 'grace', 'paid_day' or None, 'payment_due', 'paid_amount', 'tolerance', 'fee_bp', 'fee_min', 'fee_max', 'as_of'}. A payment is on time when paid_day is not None, paid_day <= due_day + grace and payment_due - paid_amount <= tolerance. Otherwise fee = clamp(round_half_up(payment_due*fee_bp/10000), fee_min, fee_max) and days_late = max(0, (paid_day or as_of when unpaid) - due_day). Return {'late', 'fee', 'days_late'}.
Why this case matters
Amortization engines drive borrower statements, payoff quotes and investor remittances; a misplaced rounding step, boundary or ordering rule compounds across hundreds of periods.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
deadline = x['due_day'] + x['grace']
paid = x['paid_day']
short = x['payment_due'] - x['paid_amount']
on_time = paid is not None and paid <= deadline and short <= x['tolerance']
if on_time:
return {'late': False, 'fee': 0, 'days_late': 0}
end = paid if paid is not None else x['as_of']
fee = rnd(short * x['fee_bp'], 10000)
fee = max(x['fee_min'], min(fee, x['fee_max']))
return {'late': True, 'fee': fee, 'days_late': max(0, end - x['due_day'])}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 25}, {'late': True, 'fee': 5000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 15, 'grace': 0, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 2500, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 800, 'days_late': 11}], ['control 4', {'due_day': 15, 'grace': 10, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 35}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 11}]], [['regression: fee base', {'due_day': 15, 'grace': 0, 'paid_day': 16, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 5000, 'days_late': 1}], ['control 1', {'due_day': 15, 'grace': 15, 'paid_day': 18, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 0, 'paid_day': 2, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 2500, 'days_late': 1}], ['control 4', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 30, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 15}], ['control 6', {'due_day': 15, 'grace': 10, 'paid_day': None, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 40}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': 5, 'payment_due': 100000, 'paid_amount': 99999, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 25}, {'late': True, 'fee': 4000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 0, 'paid_day': 14, 'payment_due': 100000, 'paid_amount': 100000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 15, 'paid_day': 16, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 15, 'paid_day': 0, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 21, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1000, 'days_late': 16}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': 6, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 100, 'days_late': 1}], ['control 1', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 150000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': None, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 5000, 'days_late': 40}], ['control 1', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 10, 'paid_day': 14, 'payment_due': 150000, 'paid_amount': 150000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 2500, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 15, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 31, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 16}], ['control 6', {'due_day': 1, 'grace': 10, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 3}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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: fee base | {'days_late': 0, 'fee': 2500, 'late': True} | {'days_late': 0, 'fee': 5000, 'late': True} | Failed |
| regression: fee base, partial-repair probe | {'days_late': 3, 'fee': 3900, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Failed |
| control 1 | {'days_late': 0, 'fee': 1500, 'late': True} | {'days_late': 0, 'fee': 1500, 'late': True} | Passed |
| control 2 | {'days_late': 0, 'fee': 0, 'late': False} | {'days_late': 0, 'fee': 0, 'late': False} | Passed |
| control 3 | {'days_late': 11, 'fee': 800, 'late': True} | {'days_late': 11, 'fee': 800, 'late': True} | Passed |
| control 4 | {'days_late': 3, 'fee': 4000, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Passed |
| control 5 | {'days_late': 11, 'fee': 1500, 'late': True} | {'days_late': 11, 'fee': 1500, 'late': True} | Passed |
SHA-256 / 8a9f2481a0d544c962bc44f412a31dbc8f30b5a9c5bcd173805cf98d609d312d
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
deadline = x['due_day'] + x['grace']
paid = x['paid_day']
short = x['payment_due'] - x['paid_amount']
on_time = paid is not None and paid <= deadline and short <= x['tolerance']
if on_time:
return {'late': False, 'fee': 0, 'days_late': 0}
end = paid if paid is not None else x['as_of']
fee = rnd(x['paid_amount'] * x['fee_bp'], 10000)
fee = max(x['fee_min'], min(fee, x['fee_max']))
return {'late': True, 'fee': fee, 'days_late': max(0, end - x['due_day'])}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 25}, {'late': True, 'fee': 5000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 15, 'grace': 0, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 2500, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 800, 'days_late': 11}], ['control 4', {'due_day': 15, 'grace': 10, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 35}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 11}]], [['regression: fee base', {'due_day': 15, 'grace': 0, 'paid_day': 16, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 5000, 'days_late': 1}], ['control 1', {'due_day': 15, 'grace': 15, 'paid_day': 18, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 0, 'paid_day': 2, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 2500, 'days_late': 1}], ['control 4', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 30, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 15}], ['control 6', {'due_day': 15, 'grace': 10, 'paid_day': None, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 40}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': 5, 'payment_due': 100000, 'paid_amount': 99999, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 25}, {'late': True, 'fee': 4000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 0, 'paid_day': 14, 'payment_due': 100000, 'paid_amount': 100000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 15, 'paid_day': 16, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 15, 'paid_day': 0, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 21, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1000, 'days_late': 16}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': 6, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 100, 'days_late': 1}], ['control 1', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 150000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': None, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 5000, 'days_late': 40}], ['control 1', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 10, 'paid_day': 14, 'payment_due': 150000, 'paid_amount': 150000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 2500, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 15, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 31, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 16}], ['control 6', {'due_day': 1, 'grace': 10, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 3}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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: fee base | {'days_late': 0, 'fee': 5000, 'late': True} | {'days_late': 0, 'fee': 5000, 'late': True} | Passed |
| regression: fee base, partial-repair probe | {'days_late': 3, 'fee': 100, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Failed |
| control 1 | {'days_late': 0, 'fee': 1500, 'late': True} | {'days_late': 0, 'fee': 1500, 'late': True} | Passed |
| control 2 | {'days_late': 0, 'fee': 0, 'late': False} | {'days_late': 0, 'fee': 0, 'late': False} | Passed |
| control 3 | {'days_late': 11, 'fee': 0, 'late': True} | {'days_late': 11, 'fee': 800, 'late': True} | Failed |
| control 4 | {'days_late': 3, 'fee': 2500, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Failed |
| control 5 | {'days_late': 11, 'fee': 5000, 'late': True} | {'days_late': 11, 'fee': 1500, 'late': True} | Failed |
SHA-256 / 45437b823b824206a1fb85b4cc34039f905135e62cb3cc6c5fe2fad32e6da957
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(x):
def rnd(n, d):
q, r = divmod(n, d)
return q + (1 if 2 * r >= d else 0)
deadline = x['due_day'] + x['grace']
paid = x['paid_day']
short = x['payment_due'] - x['paid_amount']
on_time = paid is not None and paid <= deadline and short <= x['tolerance']
if on_time:
return {'late': False, 'fee': 0, 'days_late': 0}
end = paid if paid is not None else x['as_of']
fee = rnd(x['payment_due'] * x['fee_bp'], 10000)
fee = max(x['fee_min'], min(fee, x['fee_max']))
return {'late': True, 'fee': fee, 'days_late': max(0, end - x['due_day'])}
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 25}, {'late': True, 'fee': 5000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 15, 'grace': 0, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 2500, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 800, 'days_late': 11}], ['control 4', {'due_day': 15, 'grace': 10, 'paid_day': 18, 'payment_due': 100000, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 35}, {'late': True, 'fee': 4000, 'days_late': 3}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 12, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 11}]], [['regression: fee base', {'due_day': 15, 'grace': 0, 'paid_day': 16, 'payment_due': 150000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 55}, {'late': True, 'fee': 5000, 'days_late': 1}], ['control 1', {'due_day': 15, 'grace': 15, 'paid_day': 18, 'payment_due': 20000, 'paid_amount': 100000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 5, 'grace': 0, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 0, 'paid_day': 2, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 2500, 'days_late': 1}], ['control 4', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 25}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 30, 'payment_due': 20000, 'paid_amount': 2500, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 15}], ['control 6', {'due_day': 15, 'grace': 10, 'paid_day': None, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 40}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': 5, 'payment_due': 100000, 'paid_amount': 99999, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 25}, {'late': True, 'fee': 4000, 'days_late': 0}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 1', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 0, 'paid_day': 14, 'payment_due': 100000, 'paid_amount': 100000, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 1, 'grace': 15, 'paid_day': 16, 'payment_due': 2500, 'paid_amount': 150000, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 15, 'paid_day': 0, 'payment_due': 2500, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 15, 'paid_day': 21, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 1000, 'days_late': 16}], ['regression: fee base, partial-repair probe', {'due_day': 5, 'grace': 0, 'paid_day': 6, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 0, 'fee_max': 5000, 'as_of': 45}, {'late': True, 'fee': 100, 'days_late': 1}], ['control 1', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 20000, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 15, 'paid_day': 5, 'payment_due': 20000, 'paid_amount': 99999, 'tolerance': 10, 'fee_bp': 400, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 45}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 150000, 'paid_amount': 149990, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 10000, 'as_of': 21}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 5', {'due_day': 1, 'grace': 10, 'paid_day': 1, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 0}]], [['regression: fee base', {'due_day': 5, 'grace': 10, 'paid_day': None, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 5000, 'days_late': 40}], ['control 1', {'due_day': 1, 'grace': 0, 'paid_day': 1, 'payment_due': 100000, 'paid_amount': 149990, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 5000, 'as_of': 41}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 2', {'due_day': 15, 'grace': 10, 'paid_day': 14, 'payment_due': 150000, 'paid_amount': 150000, 'tolerance': 10, 'fee_bp': 500, 'fee_min': 0, 'fee_max': 5000, 'as_of': 35}, {'late': False, 'fee': 0, 'days_late': 0}], ['control 3', {'due_day': 5, 'grace': 0, 'paid_day': 5, 'payment_due': 2500, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 45}, {'late': True, 'fee': 2500, 'days_late': 0}], ['control 4', {'due_day': 1, 'grace': 15, 'paid_day': None, 'payment_due': 2500, 'paid_amount': 20000, 'tolerance': 100, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 5000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 40}], ['control 5', {'due_day': 15, 'grace': 15, 'paid_day': 31, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 400, 'fee_min': 2500, 'fee_max': 10000, 'as_of': 55}, {'late': True, 'fee': 2500, 'days_late': 16}], ['control 6', {'due_day': 1, 'grace': 10, 'paid_day': 4, 'payment_due': 20000, 'paid_amount': 0, 'tolerance': 0, 'fee_bp': 500, 'fee_min': 1500, 'fee_max': 10000, 'as_of': 41}, {'late': True, 'fee': 1500, 'days_late': 3}]]]
for label, args, expected in fixtures[N-1]:
try:
actual = solve(args)
except Exception as exc:
actual = 'raised ' + type(exc).__name__
check(label, actual, 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: fee base | {'days_late': 0, 'fee': 5000, 'late': True} | {'days_late': 0, 'fee': 5000, 'late': True} | Passed |
| regression: fee base, partial-repair probe | {'days_late': 3, 'fee': 4000, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Passed |
| control 1 | {'days_late': 0, 'fee': 1500, 'late': True} | {'days_late': 0, 'fee': 1500, 'late': True} | Passed |
| control 2 | {'days_late': 0, 'fee': 0, 'late': False} | {'days_late': 0, 'fee': 0, 'late': False} | Passed |
| control 3 | {'days_late': 11, 'fee': 800, 'late': True} | {'days_late': 11, 'fee': 800, 'late': True} | Passed |
| control 4 | {'days_late': 3, 'fee': 4000, 'late': True} | {'days_late': 3, 'fee': 4000, 'late': True} | Passed |
| control 5 | {'days_late': 11, 'fee': 1500, 'late': True} | {'days_late': 11, 'fee': 1500, 'late': True} | Passed |
SHA-256 / 5a053d406c6d122f61459413d26cda3e06bcafc3533542490894152cd455dc64
Verification & scope
A deterministic bounded teaching model with stipulated toy lending rules stated in the contract; money is integer cents and rates are basis points; it makes no claim of conformance to any regulation, servicing standard or product. 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 2026-09-29T14:46:27.553654+00:00.
Case digest / 27b036a0b5228a85f7186fe7e6cfe4a7c95fec1a7610fc95d21b72d35cf00495