FA-68632 / Toll and parking fee computation / Member archive
Prepaid toll account auto-replenishment: the negative index is overwritten by later charges · case 02
Prepaid toll account auto-replenishment returns a wrong result when the negative index is overwritten by later charges.
Case contract
Input {balance, charges, threshold, min_replenish, usage_30d, card_ok}. The replenish amount is max(min_replenish, ceil(usage_30d/4) rounded up to a multiple of 500). After each charge, if the balance is strictly below threshold and the card works, one replenishment is added. first_negative is the index of the first charge after which the balance is negative (or null). Return {balance, replenished, first_negative}.
Why this case matters
Fee engines bill customers in integer cents; a wrong boundary, rounding stage or cap scope silently over- or under-charges.
One recorded failure
Sample boundary fixtureThis sample comes from the broken implementation of a controlled reproducer.
| Boundary fixture | Actual | Expected | Outcome |
|---|---|---|---|
| fee oracle 2 | {"balance": -525, "first_negative": 2, "replenished": 0} | {"balance": -525, "first_negative": 0, "replenished": 0} | Failed |
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