FA-59346 / Subscription proration billing / Open access

Daily plan-change proration: period length basis · case 01

Proration amounts are skewed in 31-day months and February, and exceed the plan price on annual plans.

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

ROOT CAUSE

Every period is assumed to be 30 days long instead of its actual length.

VERIFIED REPAIR

Restore the contract rule at the period length basis step: use `total = (e - s).days`.

Unsuccessful approach: The attempt uses real dates but counts the exclusive end date, shrinking every proration slightly.

Case contract

Input {old, new prices per period, start, end (exclusive), change} dates with start <= change < end. Remaining days = end - change; period days = end - start. Credit = old*remaining/period and charge = new*remaining/period, each rounded half-up. Net = charge - credit; a positive net is due now, a negative net becomes a credit balance. Return [credit, charge, amount_due, credit_balance].

Why this case matters

Mid-cycle plan changes must credit unused time on the old plan and charge the new plan for the same days.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = 30
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = charge - credit
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66])], [('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0])], [('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('additional oracle', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0])], [('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('regression', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('partial-repair probe', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression 0	`[167, 333, 166, 0]`	`[178, 357, 179, 0]`	Failed
regression 1	`[4825, 800, 0, 4025]`	`[4992, 827, 0, 4165]`	Failed
partial-repair probe 2	`[167, 333, 166, 0]`	`[56, 111, 55, 0]`	Failed
partial-repair probe 3	`[10290, 17827, 7537, 0]`	`[3430, 5942, 2512, 0]`	Failed
additional oracle 4	`[5390, 10890, 5500, 0]`	`[1797, 3630, 1833, 0]`	Failed
additional oracle 5	`[6987, 980, 0, 6007]`	`[6761, 948, 0, 5813]`	Failed
additional oracle 6	`[1288, 1222, 0, 66]`	`[1288, 1222, 0, 66]`	Passed

SHA-256 / 2ca8a2e3242d3eeb716a7a5f29a2f8bbdcdcb8b2df69e34302da4607dec2b3ba

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = (e - s).days + 1
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = charge - credit
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66])], [('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0])], [('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('additional oracle', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0])], [('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('regression', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('partial-repair probe', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression 0	`[172, 345, 173, 0]`	`[178, 357, 179, 0]`	Failed
regression 1	`[4825, 800, 0, 4025]`	`[4992, 827, 0, 4165]`	Failed
partial-repair probe 2	`[55, 110, 55, 0]`	`[56, 111, 55, 0]`	Failed
partial-repair probe 3	`[3392, 5877, 2485, 0]`	`[3430, 5942, 2512, 0]`	Failed
additional oracle 4	`[1777, 3590, 1813, 0]`	`[1797, 3630, 1833, 0]`	Failed
additional oracle 5	`[6550, 919, 0, 5631]`	`[6761, 948, 0, 5813]`	Failed
additional oracle 6	`[1246, 1183, 0, 63]`	`[1288, 1222, 0, 66]`	Failed

SHA-256 / 992779eb5667b763982609d0e72a85b8ac075073ebef6ce1bada72e88c4288e0

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import datetime
import calendar
N = 1
observations = []
def solve(x):
    s = datetime.date(*x['start'])
    e = datetime.date(*x['end'])
    c = datetime.date(*x['change'])
    total = (e - s).days
    remaining = (e - c).days
    def pr(p):
        return (p * remaining * 2 + total) // (2 * total)
    credit = pr(x['old'])
    charge = pr(x['new'])
    net = charge - credit
    return [credit, charge, max(0, net), max(0, -net)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression', {'old': 999, 'new': 1999, 'start': [2023, 10, 16], 'end': [2023, 11, 13], 'change': [2023, 11, 8]}, [178, 357, 179, 0]), ('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('partial-repair probe', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66])], [('regression', {'old': 12063, 'new': 1999, 'start': [2024, 10, 16], 'end': [2024, 11, 14], 'change': [2024, 11, 2]}, [4992, 827, 0, 4165]), ('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('partial-repair probe', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0])], [('regression', {'old': 999, 'new': 1999, 'start': [2024, 9, 16], 'end': [2024, 12, 15], 'change': [2024, 12, 10]}, [56, 111, 55, 0]), ('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0])], [('regression', {'old': 4900, 'new': 8489, 'start': [2024, 3, 22], 'end': [2024, 6, 20], 'change': [2024, 4, 18]}, [3430, 5942, 2512, 0]), ('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('partial-repair probe', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('partial-repair probe', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('additional oracle', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('additional oracle', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0])], [('regression', {'old': 4900, 'new': 9900, 'start': [2024, 1, 10], 'end': [2024, 4, 9], 'change': [2024, 3, 7]}, [1797, 3630, 1833, 0]), ('regression', {'old': 34933, 'new': 4900, 'start': [2024, 12, 28], 'end': [2025, 1, 28], 'change': [2025, 1, 22]}, [6761, 948, 0, 5813]), ('partial-repair probe', {'old': 999, 'new': 4900, 'start': [2025, 1, 22], 'end': [2025, 4, 22], 'change': [2025, 3, 8]}, [500, 2450, 1950, 0]), ('partial-repair probe', {'old': 7276, 'new': 43371, 'start': [2024, 5, 21], 'end': [2024, 8, 19], 'change': [2024, 6, 13]}, [5417, 32287, 26870, 0]), ('additional oracle', {'old': 38640, 'new': 36658, 'start': [2024, 12, 23], 'end': [2025, 1, 22], 'change': [2025, 1, 21]}, [1288, 1222, 0, 66]), ('additional oracle', {'old': 4900, 'new': 9900, 'start': [2024, 6, 18], 'end': [2024, 7, 18], 'change': [2024, 6, 21]}, [4410, 8910, 4500, 0]), ('additional oracle', {'old': 4900, 'new': 14973, 'start': [2025, 4, 11], 'end': [2025, 5, 10], 'change': [2025, 4, 17]}, [3886, 11875, 7989, 0])]]
for i, (label, args, expected) in enumerate(fixtures[N-1]):
    check("%s %d" % (label, i), solve(args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
regression 0	`[178, 357, 179, 0]`	`[178, 357, 179, 0]`	Passed
regression 1	`[4992, 827, 0, 4165]`	`[4992, 827, 0, 4165]`	Passed
partial-repair probe 2	`[56, 111, 55, 0]`	`[56, 111, 55, 0]`	Passed
partial-repair probe 3	`[3430, 5942, 2512, 0]`	`[3430, 5942, 2512, 0]`	Passed
additional oracle 4	`[1797, 3630, 1833, 0]`	`[1797, 3630, 1833, 0]`	Passed
additional oracle 5	`[6761, 948, 0, 5813]`	`[6761, 948, 0, 5813]`	Passed
additional oracle 6	`[1288, 1222, 0, 66]`	`[1288, 1222, 0, 66]`	Passed

SHA-256 / b2504556f4f3a66558183a368adb1680e3759dcdd8c4a29e07e2990c1955581c

Verification & scope

A deterministic teaching model of a stipulated billing rule. It makes no claim to reproduce any billing provider's exact behaviour and is not billing software. 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 2026-09-29T14:46:35.484850+00:00.

Case digest / f12d44c6801a449f5d1e811d22e2dc79b1f821daafb19b6eac56e9b58826b68e