FA-59361 / Subscription proration billing / Open access

Second-granular proration line items: credit line rounding direction · case 01

Credit lines ending in exactly half a cent are a cent smaller than the matching debit lines.

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

ROOT CAUSE

The negative credit is rounded half toward positive infinity instead of rounding its magnitude half-up.

VERIFIED REPAIR

Restore the contract rule at the credit line rounding direction step: use `-hu(x['old'] * x['qold'] * left)`.

Unsuccessful approach: The attempt negates a truncated magnitude, under-crediting whenever the fraction is at least one half.

Case contract

Input unix-second {start, end, change} and {old, qold, new, qnew}. If change < start or change >= end return []. Otherwise left = end - change, span = end - start. An "unused" credit line of -(old*qold*left/span) and a "remaining" line of new*qnew*left/span are emitted, each magnitude rounded half-up (half away from zero), omitting a line whose price*quantity is 0. Return [[kind, amount]].

Why this case matters

Timestamp-based proration produces separate credit and debit lines whose rounding and emission rules show on the invoice.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(x):
    if x['change'] >= x['end'] or x['change'] < x['start']:
        return []
    span = x['end'] - x['start']
    left = x['end'] - x['change']
    def hu(n):
        return (n * 2 + span) // (2 * span)
    lines = []
    if x['old'] * x['qold']:
        lines.append(['unused', hu(-x['old'] * x['qold'] * left)])
    if x['new'] * x['qnew']:
        lines.append(['remaining', hu(x['new'] * x['qnew'] * left)])
    return lines
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 3, 'qold': 1, 'new': 5, 'qnew': 1}, [['unused', -2], ['remaining', 3]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('normal control', {'start': 1718898066, 'end': 1722579184, 'change': 1721183532, 'old': 87270, 'qold': 0, 'new': 4900, 'qnew': 1}, [['remaining', 1858]]), ('normal control', {'start': 1704011568, 'end': 1706689968, 'change': 1706689968, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 3}, []), ('normal control', {'start': 1726549577, 'end': 1727154377, 'change': 1726962866, 'old': 2500, 'qold': 0, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1737228310, 'end': 1739499785, 'change': 1739499795, 'old': 178, 'qold': 1, 'new': 1500, 'qnew': 1}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('normal control', {'start': 1732894162, 'end': 1735486162, 'change': 1732894162, 'old': 1000, 'qold': 2, 'new': 91004, 'qnew': 0}, [['unused', -2000]]), ('normal control', {'start': 1749969117, 'end': 1752647517, 'change': 1751393656, 'old': 63152, 'qold': 13, 'new': 0, 'qnew': 0}, [['unused', -384330]]), ('normal control', {'start': 1728579559, 'end': 1760115559, 'change': 1760115559, 'old': 0, 'qold': 0, 'new': 51264, 'qnew': 1}, []), ('normal control', {'start': 1700089359, 'end': 1702545450, 'change': 1702420392, 'old': 79079, 'qold': 0, 'new': 0, 'qnew': 5}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('normal control', {'start': 1721814513, 'end': 1722419313, 'change': 1722419313, 'old': 0, 'qold': 3, 'new': 0, 'qnew': 5}, []), ('normal control', {'start': 1720297909, 'end': 1720623118, 'change': 1720623118, 'old': 1000, 'qold': 17, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1734629848, 'end': 1766165848, 'change': 1766165848, 'old': 1000, 'qold': 1, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1759524018, 'end': 1763871464, 'change': 1759976835, 'old': 0, 'qold': 0, 'new': 1500, 'qnew': 5}, [['remaining', 6719]])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe', {'start': 1734436882, 'end': 1765972882, 'change': 1756322121, 'old': 10374, 'qold': 1, 'new': 4900, 'qnew': 1}, [['unused', -3175], ['remaining', 1500]]), ('partial-repair probe', {'start': 1742110108, 'end': 1745693685, 'change': 1744431348, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 5}, [['unused', -881], ['remaining', 2642]]), ('normal control', {'start': 1759898518, 'end': 1762576918, 'change': 1760952409, 'old': 0, 'qold': 3, 'new': 37669, 'qnew': 0}, []), ('normal control', {'start': 1724743049, 'end': 1756279049, 'change': 1724743049, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 1}, [['unused', -2500], ['remaining', 1500]]), ('normal control', {'start': 1742436208, 'end': 1773972208, 'change': 1773972218, 'old': 0, 'qold': 3, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1757847857, 'end': 1760439857, 'change': 1757847852, 'old': 92286, 'qold': 0, 'new': 0, 'qnew': 4}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('partial-repair probe', {'start': 1714042904, 'end': 1745578904, 'change': 1717176355, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 0}, [['unused', -2702]]), ('partial-repair probe', {'start': 1749513307, 'end': 1752191707, 'change': 1749624391, 'old': 37053, 'qold': 11, 'new': 0, 'qnew': 0}, [['unused', -390679]]), ('normal control', {'start': 1726496239, 'end': 1729174639, 'change': 1726496239, 'old': 73990, 'qold': 3, 'new': 47429, 'qnew': 5}, [['unused', -221970], ['remaining', 237145]]), ('normal control', {'start': 1739738740, 'end': 1771274740, 'change': 1771274740, 'old': 2500, 'qold': 3, 'new': 1500, 'qnew': 5}, []), ('normal control', {'start': 1725551908, 'end': 1757087908, 'change': 1757087918, 'old': 67119, 'qold': 3, 'new': 4900, 'qnew': 13}, []), ('normal control', {'start': 1753105090, 'end': 1753709890, 'change': 1753105090, 'old': 1000, 'qold': 0, 'new': 0, 'qnew': 1}, [])]]
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 (boundary) 0	`[['unused', -1], ['remaining', 3]]`	`[['unused', -2], ['remaining', 3]]`	Failed
regression (boundary) 1	`[['unused', -2], ['remaining', 4]]`	`[['unused', -3], ['remaining', 4]]`	Failed
partial-repair probe (boundary) 2	`[['unused', -3], ['remaining', 5]]`	`[['unused', -4], ['remaining', 5]]`	Failed
partial-repair probe (boundary) 3	`[['unused', -4], ['remaining', 6]]`	`[['unused', -5], ['remaining', 6]]`	Failed
normal control 4	`[['remaining', 1858]]`	`[['remaining', 1858]]`	Passed
normal control 5	`[]`	`[]`	Passed
normal control 6	`[]`	`[]`	Passed
normal control 7	`[]`	`[]`	Passed

SHA-256 / 79806227e71f5def6510615000486486b17367179223b4e36b22bfb059a874c7

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(x):
    if x['change'] >= x['end'] or x['change'] < x['start']:
        return []
    span = x['end'] - x['start']
    left = x['end'] - x['change']
    def hu(n):
        return (n * 2 + span) // (2 * span)
    lines = []
    if x['old'] * x['qold']:
        lines.append(['unused', -(x['old'] * x['qold'] * left // span)])
    if x['new'] * x['qnew']:
        lines.append(['remaining', hu(x['new'] * x['qnew'] * left)])
    return lines
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 3, 'qold': 1, 'new': 5, 'qnew': 1}, [['unused', -2], ['remaining', 3]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('normal control', {'start': 1718898066, 'end': 1722579184, 'change': 1721183532, 'old': 87270, 'qold': 0, 'new': 4900, 'qnew': 1}, [['remaining', 1858]]), ('normal control', {'start': 1704011568, 'end': 1706689968, 'change': 1706689968, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 3}, []), ('normal control', {'start': 1726549577, 'end': 1727154377, 'change': 1726962866, 'old': 2500, 'qold': 0, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1737228310, 'end': 1739499785, 'change': 1739499795, 'old': 178, 'qold': 1, 'new': 1500, 'qnew': 1}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('normal control', {'start': 1732894162, 'end': 1735486162, 'change': 1732894162, 'old': 1000, 'qold': 2, 'new': 91004, 'qnew': 0}, [['unused', -2000]]), ('normal control', {'start': 1749969117, 'end': 1752647517, 'change': 1751393656, 'old': 63152, 'qold': 13, 'new': 0, 'qnew': 0}, [['unused', -384330]]), ('normal control', {'start': 1728579559, 'end': 1760115559, 'change': 1760115559, 'old': 0, 'qold': 0, 'new': 51264, 'qnew': 1}, []), ('normal control', {'start': 1700089359, 'end': 1702545450, 'change': 1702420392, 'old': 79079, 'qold': 0, 'new': 0, 'qnew': 5}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('normal control', {'start': 1721814513, 'end': 1722419313, 'change': 1722419313, 'old': 0, 'qold': 3, 'new': 0, 'qnew': 5}, []), ('normal control', {'start': 1720297909, 'end': 1720623118, 'change': 1720623118, 'old': 1000, 'qold': 17, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1734629848, 'end': 1766165848, 'change': 1766165848, 'old': 1000, 'qold': 1, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1759524018, 'end': 1763871464, 'change': 1759976835, 'old': 0, 'qold': 0, 'new': 1500, 'qnew': 5}, [['remaining', 6719]])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe', {'start': 1734436882, 'end': 1765972882, 'change': 1756322121, 'old': 10374, 'qold': 1, 'new': 4900, 'qnew': 1}, [['unused', -3175], ['remaining', 1500]]), ('partial-repair probe', {'start': 1742110108, 'end': 1745693685, 'change': 1744431348, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 5}, [['unused', -881], ['remaining', 2642]]), ('normal control', {'start': 1759898518, 'end': 1762576918, 'change': 1760952409, 'old': 0, 'qold': 3, 'new': 37669, 'qnew': 0}, []), ('normal control', {'start': 1724743049, 'end': 1756279049, 'change': 1724743049, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 1}, [['unused', -2500], ['remaining', 1500]]), ('normal control', {'start': 1742436208, 'end': 1773972208, 'change': 1773972218, 'old': 0, 'qold': 3, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1757847857, 'end': 1760439857, 'change': 1757847852, 'old': 92286, 'qold': 0, 'new': 0, 'qnew': 4}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('partial-repair probe', {'start': 1714042904, 'end': 1745578904, 'change': 1717176355, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 0}, [['unused', -2702]]), ('partial-repair probe', {'start': 1749513307, 'end': 1752191707, 'change': 1749624391, 'old': 37053, 'qold': 11, 'new': 0, 'qnew': 0}, [['unused', -390679]]), ('normal control', {'start': 1726496239, 'end': 1729174639, 'change': 1726496239, 'old': 73990, 'qold': 3, 'new': 47429, 'qnew': 5}, [['unused', -221970], ['remaining', 237145]]), ('normal control', {'start': 1739738740, 'end': 1771274740, 'change': 1771274740, 'old': 2500, 'qold': 3, 'new': 1500, 'qnew': 5}, []), ('normal control', {'start': 1725551908, 'end': 1757087908, 'change': 1757087918, 'old': 67119, 'qold': 3, 'new': 4900, 'qnew': 13}, []), ('normal control', {'start': 1753105090, 'end': 1753709890, 'change': 1753105090, 'old': 1000, 'qold': 0, 'new': 0, 'qnew': 1}, [])]]
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 (boundary) 0	`[['unused', -1], ['remaining', 3]]`	`[['unused', -2], ['remaining', 3]]`	Failed
regression (boundary) 1	`[['unused', -2], ['remaining', 4]]`	`[['unused', -3], ['remaining', 4]]`	Failed
partial-repair probe (boundary) 2	`[['unused', -3], ['remaining', 5]]`	`[['unused', -4], ['remaining', 5]]`	Failed
partial-repair probe (boundary) 3	`[['unused', -4], ['remaining', 6]]`	`[['unused', -5], ['remaining', 6]]`	Failed
normal control 4	`[['remaining', 1858]]`	`[['remaining', 1858]]`	Passed
normal control 5	`[]`	`[]`	Passed
normal control 6	`[]`	`[]`	Passed
normal control 7	`[]`	`[]`	Passed

SHA-256 / 6cf4588680307222fa304800a3410096202b65d9581928fef775428f78dc2f52

3 / The verified repair

Exit 0

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

N = 1
observations = []
def solve(x):
    if x['change'] >= x['end'] or x['change'] < x['start']:
        return []
    span = x['end'] - x['start']
    left = x['end'] - x['change']
    def hu(n):
        return (n * 2 + span) // (2 * span)
    lines = []
    if x['old'] * x['qold']:
        lines.append(['unused', -hu(x['old'] * x['qold'] * left)])
    if x['new'] * x['qnew']:
        lines.append(['remaining', hu(x['new'] * x['qnew'] * left)])
    return lines
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 3, 'qold': 1, 'new': 5, 'qnew': 1}, [['unused', -2], ['remaining', 3]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('normal control', {'start': 1718898066, 'end': 1722579184, 'change': 1721183532, 'old': 87270, 'qold': 0, 'new': 4900, 'qnew': 1}, [['remaining', 1858]]), ('normal control', {'start': 1704011568, 'end': 1706689968, 'change': 1706689968, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 3}, []), ('normal control', {'start': 1726549577, 'end': 1727154377, 'change': 1726962866, 'old': 2500, 'qold': 0, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1737228310, 'end': 1739499785, 'change': 1739499795, 'old': 178, 'qold': 1, 'new': 1500, 'qnew': 1}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 5, 'qold': 1, 'new': 7, 'qnew': 1}, [['unused', -3], ['remaining', 4]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('normal control', {'start': 1732894162, 'end': 1735486162, 'change': 1732894162, 'old': 1000, 'qold': 2, 'new': 91004, 'qnew': 0}, [['unused', -2000]]), ('normal control', {'start': 1749969117, 'end': 1752647517, 'change': 1751393656, 'old': 63152, 'qold': 13, 'new': 0, 'qnew': 0}, [['unused', -384330]]), ('normal control', {'start': 1728579559, 'end': 1760115559, 'change': 1760115559, 'old': 0, 'qold': 0, 'new': 51264, 'qnew': 1}, []), ('normal control', {'start': 1700089359, 'end': 1702545450, 'change': 1702420392, 'old': 79079, 'qold': 0, 'new': 0, 'qnew': 5}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 7, 'qold': 1, 'new': 9, 'qnew': 1}, [['unused', -4], ['remaining', 5]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('normal control', {'start': 1721814513, 'end': 1722419313, 'change': 1722419313, 'old': 0, 'qold': 3, 'new': 0, 'qnew': 5}, []), ('normal control', {'start': 1720297909, 'end': 1720623118, 'change': 1720623118, 'old': 1000, 'qold': 17, 'new': 0, 'qnew': 0}, []), ('normal control', {'start': 1734629848, 'end': 1766165848, 'change': 1766165848, 'old': 1000, 'qold': 1, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1759524018, 'end': 1763871464, 'change': 1759976835, 'old': 0, 'qold': 0, 'new': 1500, 'qnew': 5}, [['remaining', 6719]])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 9, 'qold': 1, 'new': 11, 'qnew': 1}, [['unused', -5], ['remaining', 6]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('partial-repair probe', {'start': 1734436882, 'end': 1765972882, 'change': 1756322121, 'old': 10374, 'qold': 1, 'new': 4900, 'qnew': 1}, [['unused', -3175], ['remaining', 1500]]), ('partial-repair probe', {'start': 1742110108, 'end': 1745693685, 'change': 1744431348, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 5}, [['unused', -881], ['remaining', 2642]]), ('normal control', {'start': 1759898518, 'end': 1762576918, 'change': 1760952409, 'old': 0, 'qold': 3, 'new': 37669, 'qnew': 0}, []), ('normal control', {'start': 1724743049, 'end': 1756279049, 'change': 1724743049, 'old': 2500, 'qold': 1, 'new': 1500, 'qnew': 1}, [['unused', -2500], ['remaining', 1500]]), ('normal control', {'start': 1742436208, 'end': 1773972208, 'change': 1773972218, 'old': 0, 'qold': 3, 'new': 4900, 'qnew': 1}, []), ('normal control', {'start': 1757847857, 'end': 1760439857, 'change': 1757847852, 'old': 92286, 'qold': 0, 'new': 0, 'qnew': 4}, [])], [('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 11, 'qold': 1, 'new': 13, 'qnew': 1}, [['unused', -6], ['remaining', 7]]), ('regression (boundary)', {'start': 1000, 'end': 2000, 'change': 1500, 'old': 13, 'qold': 1, 'new': 15, 'qnew': 1}, [['unused', -7], ['remaining', 8]]), ('partial-repair probe', {'start': 1714042904, 'end': 1745578904, 'change': 1717176355, 'old': 1000, 'qold': 3, 'new': 1500, 'qnew': 0}, [['unused', -2702]]), ('partial-repair probe', {'start': 1749513307, 'end': 1752191707, 'change': 1749624391, 'old': 37053, 'qold': 11, 'new': 0, 'qnew': 0}, [['unused', -390679]]), ('normal control', {'start': 1726496239, 'end': 1729174639, 'change': 1726496239, 'old': 73990, 'qold': 3, 'new': 47429, 'qnew': 5}, [['unused', -221970], ['remaining', 237145]]), ('normal control', {'start': 1739738740, 'end': 1771274740, 'change': 1771274740, 'old': 2500, 'qold': 3, 'new': 1500, 'qnew': 5}, []), ('normal control', {'start': 1725551908, 'end': 1757087908, 'change': 1757087918, 'old': 67119, 'qold': 3, 'new': 4900, 'qnew': 13}, []), ('normal control', {'start': 1753105090, 'end': 1753709890, 'change': 1753105090, 'old': 1000, 'qold': 0, 'new': 0, 'qnew': 1}, [])]]
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 (boundary) 0	`[['unused', -2], ['remaining', 3]]`	`[['unused', -2], ['remaining', 3]]`	Passed
regression (boundary) 1	`[['unused', -3], ['remaining', 4]]`	`[['unused', -3], ['remaining', 4]]`	Passed
partial-repair probe (boundary) 2	`[['unused', -4], ['remaining', 5]]`	`[['unused', -4], ['remaining', 5]]`	Passed
partial-repair probe (boundary) 3	`[['unused', -5], ['remaining', 6]]`	`[['unused', -5], ['remaining', 6]]`	Passed
normal control 4	`[['remaining', 1858]]`	`[['remaining', 1858]]`	Passed
normal control 5	`[]`	`[]`	Passed
normal control 6	`[]`	`[]`	Passed
normal control 7	`[]`	`[]`	Passed

SHA-256 / f55c8fdd8134a162d360597b47e71156edba59af4d520f8bf96e2951ae35734d

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 2026-09-29T14:46:35.525367+00:00.

Case digest / 0f6f88461ad60d49378a0b16aca77cbaad16234b18d3f9fb0839b291c51f8419