import 'package:flutter_test/flutter_test.dart';
import 'package:fuel_tax_tracker/services/estimated_refund.dart';

void main() {
  test('the rate itself is 12.5 cents per gallon', () {
    expect(moHighwayFuelTaxRefundRatePerGallon, 0.125);
  });

  test('multiplies whole gallons by the rate', () {
    expect(estimatedFuelRefund(10), 1.25);
    expect(estimatedFuelRefund(20), 2.50);
    expect(estimatedFuelRefund(0), 0);
  });

  test('rounds fractional gallons to the nearest whole gallon before multiplying', () {
    // 10.523 rounds up to 11 gallons: 11 * $0.125 = $1.375, floored to $1.37.
    expect(estimatedFuelRefund(10.523), 1.37);
    // 10.4 rounds down to 10 gallons: 10 * $0.125 = $1.25 exactly.
    expect(estimatedFuelRefund(10.4), 1.25);
  });

  test('rounds the resulting cents down, never up', () {
    // 1 gallon * $0.125 = $0.125 — rounding to the nearest cent would give
    // $0.13, but this must floor to $0.12 instead.
    expect(estimatedFuelRefund(1), 0.12);
    // 3 gallons * $0.125 = $0.375 — floors to $0.37, not $0.38.
    expect(estimatedFuelRefund(3), 0.37);
  });
}