FA-85389 / Ride-hailing fare and surge pricing / Member archive

Promo percentage applied to the booking fee · case 04

Percentage promos are larger than advertised because they include the fee.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Cents throughout. Surge (tenths) multiplies only base+distance+time, rounded half up. A percentage promo discounts the surged amount (floor), capped at promo cap cents. The booking fee is added after the discount. Tax (basis points, rounded half up) applies to surged - discount + booking fee; tolls and airport fees are passed through untaxed and unsurged.

Why this case matters

Ride-hailing prices are computed per trip at scale; ordering, unit and boundary slips become systematic over- or under-charging.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: promo base	`{"discount": 500, "surged": 2438, "tax": 136, "total": 2319}`	`{"discount": 487, "surged": 2438, "tax": 137, "total": 2333}`	Failed

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