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Worth the Drive: calculation audit + listing/detail polish

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Calculation audit (brief config: 30 MPG imperial, £60 fill-up, baseline
Rontec Shelf 171.9p at 0.4 mi):

- One mile<->kilometre constant pair (kilometresPerMile 1.609344,
  metresPerMile 1609.344) replaces the mixed 1609.34 / 0.621371 / 1.60934
  used in the savings path. Effect ~2 ppm (invisible), but the conversions
  are now auditable in one place.
- New FuelSavingsCalculationAuditTests (20 deterministic tests, no live
  MKDirections) pins the brief's three stations - Tesco 170.9p/2.0 mi,
  MFG Hare & Hounds 172.9p/2.8 mi, PGG Napoleon 171.9p/2.8 mi - plus
  imperial-vs-US gallon, MPG and budget scaling, the break-even tolerance
  boundary, the nearer-candidate clamp, route-unavailable, mixed-basis
  estimates and display-rounding boundaries.
- Formula unchanged, and verified correct: fixed quantity (budget / baseline
  price), pump saving, round-trip extra distance clamped at zero, travel fuel
  priced at the candidate station, +/-5p break even, baseline labelled
  "Closest station", sorting on the unrounded net saving. The brief's "£0.18"
  for Tesco is the rounded 1 dp extra-distance caption (2.02-2.05 mi reads as
  "2.0 mi"), not a rounding bug in the money.

UI (uncommitted since d7a0ecb):

- Done bar drawn in the bottom safe area from keyboard notifications:
  .toolbar(placement: .keyboard) is device-dependent (present on the 15 Pro,
  absent on the SE on the same iOS build).
- Favourite star in the More-info heading, wired to the same fuel-scoped
  toggle as the listing rows at all three call sites.
- CHEAPEST/TOP badge moved above the price so it reads as part of it.
- Listing rows carry the real session fill-up amount instead of a hard zero
  (the compact banner does not print it today; a future row layout would).

153 tests, 0 failures. Simulator and device builds succeed.
This commit is contained in:
FuelBoard Contributor
2026-10-11 17:19:10 +01:00
parent d7a0ecb79a
commit d0a89d97d5
10 changed files with 780 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files
FuelBoard/ContentView.swift
+67 -18
View File
@@ -296,7 +296,7 @@ struct ContentView: View {
/// that every station the app lists can carry a saving.
private func savingsJourneyMiles(for station: FuelStation, location: Coordinate) -> FuelSavingsJourney? {
if let roadMeters = FuelStore.roadJourneyMeters(for: station, userLat: location.lat, userLng: location.lng) {
return FuelSavingsJourney(miles: roadMeters / 1609.34, basis: .roadRoute)
return FuelSavingsJourney(miles: roadMeters / FuelSavingsCalculator.metresPerMile, basis: .roadRoute)
}
return FuelSavingsJourney(
miles: savingsFallbackMiles(for: station, location: location),
@@ -305,7 +305,7 @@ struct ContentView: View {
}
private func savingsFallbackMiles(for station: FuelStation, location: Coordinate) -> Double {
FuelStore.displayDistanceKM(station: station, userLat: location.lat, userLng: location.lng) * 0.621371 * 2
FuelStore.displayDistanceKM(station: station, userLat: location.lat, userLng: location.lng) / FuelSavingsCalculator.kilometresPerMile * 2
}
private func sortedForWorthTheDrive(_ pool: [FuelStation]) -> [FuelStation] {
@@ -424,7 +424,12 @@ struct ContentView: View {
StationDetailView(
station: station,
location: location,
distanceUnit: distanceUnit
distanceUnit: distanceUnit,
fuelSavings: savingsLookup(baseline: nearestSavingsBaseline)(station),
fuelSavingsAmount: sessionFuelSavingsAmount,
savingsBaselineStationName: nearestSavingsBaseline?.name,
isFavourite: favouriteIDs.contains(station.id),
onToggleFavourite: { toggleFavourite(station, fuel: selectedFuel) }
)
}
.onReceive(NotificationCenter.default.publisher(for: .fuelBoardShowStationDetail)) { note in
@@ -525,6 +530,13 @@ struct ContentView: View {
fuelSavingsSettings = forced
sortMode = .worthTheDrive
}
// QA temp: `FB_DETAIL_DEBUG=1` (DEBUG builds only) forces
// "Tap station = More info". The stored default is open-Apple-Maps,
// so on a simulator a tap bounces out to Maps with no way back and
// the Worth the Drive detail section can't be checked at all.
if ProcessInfo.processInfo.environment["FB_DETAIL_DEBUG"] == "1" {
stationTapAction = .showDetails
}
// `-forceOfflineDump` / `-forceConnectionProblem` simulate the two
// failure legs for the screenshot harness. The auto-refresh below
// is skipped so the banner stays up (a live fetch would clear it).
@@ -1242,6 +1254,10 @@ struct StationRow: View {
var topBadgeText: String = "TOP"
var tapAction: StationTapAction = .openMap
var fuelSavings: FuelSavingsAvailability?
/// The session fill-up figure (the one the adjustment control edits). The
/// compact banner does not print it today, but a row that carried a hard
/// zero would print "for £0" the moment it did — pass the real figure.
var fuelSavingsAmount: FuelSavingsFillAmount = FuelSavingsSettings.defaultPreferredAmount
var onToggleFavourite: () -> Void = {}
var onShowDetails: (FuelStation) -> Void = { _ in }
@@ -1263,6 +1279,13 @@ struct StationRow: View {
return String(format: "%+.1fp", delta)
}
/// True when this row IS the cheapest in range — its delta reads "best",
/// so labelling it "vs cheapest" would be nonsense.
private var isCheapestPrice: Bool {
guard let price = station.prices[fuel], let baselinePrice else { return false }
return abs(price - baselinePrice) <= 0.05
}
private func handleTap() {
switch tapAction {
case .openMap:
@@ -1279,6 +1302,7 @@ struct StationRow: View {
}
var body: some View {
VStack(alignment: .leading, spacing: 6) {
HStack(spacing: 12) {
// LEFT — round brand logo (or generic fuel pump fallback)
Group {
@@ -1306,18 +1330,6 @@ struct StationRow: View {
.font(.headline)
.lineLimit(1)
.truncationMode(.tail)
if isTopResult {
// The badge always marks the CHEAPEST PUMP PRICE (never
// "best saving"), so in Worth the Drive order — where
// the top row is the best net saving — it may sit lower
// down the list, and says so.
Text(topBadgeText)
.font(.caption2.bold())
.padding(.horizontal, 5)
.padding(.vertical, 1)
.background(Capsule().fill(.blue.opacity(0.15)))
.foregroundStyle(.blue)
}
ForEach(StationNotice.notices(for: station)) { notice in
Image(systemName: notice.symbolName)
.font(.caption2.weight(.semibold))
@@ -1336,14 +1348,27 @@ struct StationRow: View {
.foregroundStyle(.secondary)
.monospacedDigit()
}
if fuelSavings != nil {
FuelSavingsSummaryView(availability: fuelSavings, amount: .init(value: 0, unit: .pounds), baselineStationName: nil, compact: true)
}
}
.frame(maxWidth: .infinity, alignment: .leading)
// RIGHT — price in £ (no p) + difference vs cheapest
VStack(alignment: .trailing, spacing: 2) {
if isTopResult {
// The badge always marks the CHEAPEST PUMP PRICE (never
// "best saving"), so in Worth the Drive order — where the
// top row is the best net saving — it may sit lower down
// the list, and says so. It sits ABOVE the price it
// annotates rather than beside the name, so it reads as
// part of the price and the name keeps its width.
Text(topBadgeText)
.font(.caption2.bold())
.padding(.horizontal, 5)
.padding(.vertical, 1)
.background(Capsule().fill(.blue.opacity(0.15)))
.foregroundStyle(.blue)
.lineLimit(1)
.fixedSize()
}
if let price = station.prices[fuel] {
HStack(spacing: 5) {
Circle()
@@ -1355,6 +1380,16 @@ struct StationRow: View {
Text(deltaText)
.font(.caption2.bold().monospaced())
.foregroundStyle(ragColor)
if !isCheapestPrice {
// "+8.0p" on its own never said what it measured
// against; the delta is against the cheapest price
// in range in EVERY sort mode.
Text("vs cheapest")
.font(.caption2)
.foregroundStyle(.secondary)
.lineLimit(1)
.minimumScaleFactor(0.8)
}
}
}
}
@@ -1368,6 +1403,20 @@ struct StationRow: View {
}
.buttonStyle(.borderless)
}
if fuelSavings != nil {
// Full-width verdict banner under the row. Inline in the middle
// column it truncated ("Save £2.75 after tra…") because the
// price block squeezes that column — and the verdict is the
// point of this sort mode, so it gets its own line.
FuelSavingsSummaryView(
availability: fuelSavings,
amount: fuelSavingsAmount,
baselineStationName: nil,
compact: true,
distanceUnit: distanceUnit
)
}
}
.contentShape(Rectangle())
.onTapGesture(perform: handleTap)
.onLongPressGesture(perform: showDetails)
FuelBoard/FavouritesView.swift
+6 -1
View File
@@ -167,6 +167,7 @@ struct FavouritesView: View {
topBadgeText: "CHEAPEST",
tapAction: stationTapAction,
fuelSavings: savingsForStation(station),
fuelSavingsAmount: fuelSavingsAmount,
onToggleFavourite: { onToggleFavourite(station, activeFuel) },
onShowDetails: { detailStation = $0 }
)
@@ -217,7 +218,11 @@ struct FavouritesView: View {
distanceUnit: distanceUnit,
fuelSavings: savingsForStation(station),
fuelSavingsAmount: fuelSavingsAmount,
savingsBaselineStationName: savingsBaselineStationName
savingsBaselineStationName: savingsBaselineStationName,
// Every station listed here IS a favourite for the tab's
// fuel, so the star starts filled; tapping it unstars.
isFavourite: true,
onToggleFavourite: { onToggleFavourite(station, activeFuel) }
)
}
.onAppear {
FuelBoard/FuelSavingsViews.swift
+90 -8
View File
@@ -5,6 +5,10 @@ struct FuelSavingsAdjustmentView: View {
let referencePricePencePerLitre: Double?
@State private var textValue: String = ""
/// Focus for the numeric field — also lets the DEBUG QA hook below raise the
/// keyboard on launch so the Done bar can be screenshotted (a script cannot
/// tap the simulator).
@FocusState private var isAmountFieldFocused: Bool
private var range: ClosedRange<Double> {
amount.unit == .pounds ? 10...100 : 10...80
@@ -27,12 +31,25 @@ struct FuelSavingsAdjustmentView: View {
.multilineTextAlignment(.trailing)
.frame(width: 72)
.textFieldStyle(.roundedBorder)
.focused($isAmountFieldFocused)
.accessibilityIdentifier("fillAmountField")
}
Text("Changes the estimate for this session only — your Settings default stays unchanged.")
.font(.caption2)
.foregroundStyle(.secondary)
}
.onAppear { syncText() }
.onAppear {
syncText()
#if DEBUG
// QA hook: raise the keyboard without a tap so the Done bar can be
// screenshotted on a simulator (synthetic taps do not reach it).
if ProcessInfo.processInfo.arguments.contains("-focusFillAmount") {
DispatchQueue.main.asyncAfter(deadline: .now() + 1.0) {
isAmountFieldFocused = true
}
}
#endif
}
.onChange(of: amount.value) { _, _ in syncText() }
.onChange(of: amount.unit) { _, _ in syncText() }
}
@@ -83,16 +100,53 @@ struct FuelSavingsSummaryView: View {
let amount: FuelSavingsFillAmount
let baselineStationName: String?
var compact: Bool = false
/// Sizes the "more driving than closest" caption in the user's own unit (the
/// stored figure is miles) — used by both the row banner and the detail sheet.
var distanceUnit: DistanceUnit = .miles
var body: some View {
switch availability {
case .available(let result):
VStack(alignment: .leading, spacing: compact ? 2 : 8) {
Label(result.status.displayName, systemImage: symbol(for: result.status))
.font(compact ? .caption.weight(.semibold) : .headline)
Text(result.headline(compact: compact))
.font(compact ? .caption2.bold().monospacedDigit() : .subheadline.bold().monospacedDigit())
if !compact {
if compact {
// FULL-WIDTH banner under the row. Inline inside the middle
// column the capsule truncated ("Save £2.75 after tra…") because
// the column is squeezed by the price block — the verdict is the
// point of this sort mode, so it gets its own line with room.
// Colour carries the verdict: green save, red worse off, grey
// break even, blue baseline. lineLimit + minimumScaleFactor keep
// it to one line, so rows stay even.
VStack(alignment: .leading, spacing: 2) {
capsule(for: result, compact: true)
if let extraTravel = FuelSavingsFormat.extraTravelLabel(
extraDistanceMiles: result.extraDistanceMiles,
unit: distanceUnit
) {
Text(extraTravel)
.font(.caption2)
.foregroundStyle(.secondary)
.lineLimit(1)
.minimumScaleFactor(0.85)
}
}
// Aligns the banner with the row's text column (46 pt logo + 12
// pt spacing) so it reads as part of the row, not the cell.
.padding(.leading, 58)
} else {
// Detail sheet: the SAME verdict capsule and the SAME caption as
// the listing rows (one implementation, so wording and colour
// cannot drift), followed by the breakdown only this view has
// room for. The old shape led with a status word + headline that
// matched neither the listing nor each other.
VStack(alignment: .leading, spacing: 10) {
capsule(for: result, compact: false)
if let extraTravel = FuelSavingsFormat.extraTravelLabel(
extraDistanceMiles: result.extraDistanceMiles,
unit: distanceUnit
) {
Text(extraTravel)
.font(.subheadline)
.foregroundStyle(.secondary)
}
if result.status == .baseline {
Text("Your closest station with a price for this fuel — every other saving is measured against it.")
.font(.caption)
@@ -101,7 +155,6 @@ struct FuelSavingsSummaryView: View {
Text("Compared with \(baselineStationName ?? "your nearest station") for \(amountText).").font(.caption).foregroundStyle(.secondary)
LabeledContent("Fuel-price saving", value: FuelSavingsFormat.money(result.grossSavingGBP))
LabeledContent("Extra driving cost", value: FuelSavingsFormat.money(result.extraDrivingCostGBP))
LabeledContent("Extra distance", value: String(format: "%.1f miles", result.extraDistanceMiles))
if result.distanceBasis.isEstimate {
Text("Estimated from straight-line distance — refined once the route is measured.")
.font(.caption2)
@@ -129,6 +182,35 @@ struct FuelSavingsSummaryView: View {
}
}
/// The colour-coded verdict capsule — ONE implementation for the listing rows
/// and the detail sheet, so the verdict reads identically in both; the sheet
/// just gets the larger font and padding.
private func capsule(for result: FuelSavingsResult, compact: Bool) -> some View {
Label {
Text(result.capsuleHeadline())
.lineLimit(1)
.minimumScaleFactor(0.8)
} icon: {
Image(systemName: symbol(for: result.status))
}
.font(compact ? .caption.weight(.semibold) : .headline)
.foregroundStyle(capsuleColor(for: result.status))
.padding(.horizontal, compact ? 8 : 12)
.padding(.vertical, compact ? 4 : 7)
.background(Capsule().fill(capsuleColor(for: result.status).opacity(0.15)))
}
/// Verdict colour: green save, red worse off, grey break even, blue
/// baseline — the same green/amber/red family the price dot already uses.
private func capsuleColor(for status: FuelSavingsStatus) -> Color {
switch status {
case .worthTheDrive: return .green
case .notWorthTheDrive: return .red
case .breakEven: return .secondary
case .baseline: return .blue
}
}
private func symbol(for status: FuelSavingsStatus) -> String {
switch status {
case .worthTheDrive: return "checkmark.circle.fill"
FuelBoard/KeyboardSupport.swift
+45 -7
View File
@@ -1,5 +1,6 @@
import SwiftUI
import UIKit
import Combine
extension View {
/// Puts a Done button above the keyboard.
@@ -11,17 +12,41 @@ extension View {
/// `TextField(value:format:)` only commits the typed value when editing
/// ends — so the number never stuck either.
///
/// Apply ONCE per screen, to the list or form containing the fields: the
/// keyboard toolbar belongs to the focused field, so a single attachment
/// covers every field inside it. Attaching it to each field would show
/// several Done buttons at once.
/// WHY IT IS DRAWN HERE RATHER THAN AS `.toolbar(placement: .keyboard)`:
/// the keyboard-toolbar form is device-dependent. The same build showed the
/// Done button on the iPhone 15 Pro and NOT on the iPhone SE (both iOS
/// 27.0.1, same install, same binary), leaving the SE with no way to
/// dismiss or commit a numeric field. Drawing the bar in the screen's own
/// bottom safe area renders identically on every device, so the accessibility
/// of the numeric fields no longer depends on the accessory view appearing.
///
/// Apply ONCE per screen, to the list or form containing the fields: any
/// keyboard on that screen shows the bar, so attaching it to each field
/// would stack several Done buttons.
///
/// - Parameter action: clears the screen's focus state. Prefer this where a
/// `@FocusState` exists; the default resigns the current first responder,
/// which works for fields inside subviews that have no focus binding.
/// which works for fields inside subviews that have no focus binding (the
/// fill-up box in the station list is one).
func keyboardDoneButton(action: (() -> Void)? = nil) -> some View {
toolbar {
ToolbarItemGroup(placement: .keyboard) {
modifier(KeyboardDoneBar(action: action))
}
}
/// Shows a Done bar while a keyboard is up on this screen.
///
/// Visibility comes from the keyboard notifications rather than a `@FocusState`
/// so the bar also works for fields inside subviews that have no focus binding.
private struct KeyboardDoneBar: ViewModifier {
let action: (() -> Void)?
@State private var isKeyboardVisible = false
func body(content: Content) -> some View {
content
.safeAreaInset(edge: .bottom, spacing: 0) {
if isKeyboardVisible {
HStack {
Spacer()
Button("Done") {
if let action {
@@ -34,8 +59,21 @@ extension View {
for: nil
)
}
isKeyboardVisible = false
}
.font(.body.weight(.semibold))
}
.padding(.horizontal, 20)
.padding(.vertical, 10)
.frame(maxWidth: .infinity)
.background(.bar)
}
}
.onReceive(NotificationCenter.default.publisher(for: UIResponder.keyboardWillShowNotification)) { _ in
isKeyboardVisible = true
}
.onReceive(NotificationCenter.default.publisher(for: UIResponder.keyboardWillHideNotification)) { _ in
isKeyboardVisible = false
}
}
}
FuelBoard/StationDetailView.swift
+22 -1
View File
@@ -13,6 +13,12 @@ struct StationDetailView: View {
var fuelSavings: FuelSavingsAvailability? = nil
var fuelSavingsAmount: FuelSavingsFillAmount = FuelSavingsSettings.defaultPreferredAmount
var savingsBaselineStationName: String? = nil
/// Whether this station is starred for the fuel currently being viewed, and
/// the toggle that flips it. Passed from the list that opened the sheet, so
/// the star here and the star on the row are the same fuel-scoped
/// favourite and cannot drift apart.
var isFavourite: Bool = false
var onToggleFavourite: (() -> Void)? = nil
@Environment(\.dismiss) private var dismiss
@State private var showingReportIssueConfirmation = false
@@ -61,7 +67,8 @@ struct StationDetailView: View {
FuelSavingsSummaryView(
availability: fuelSavings,
amount: fuelSavingsAmount,
baselineStationName: savingsBaselineStationName
baselineStationName: savingsBaselineStationName,
distanceUnit: distanceUnit
)
} header: {
Text("Worth the drive?")
@@ -96,6 +103,20 @@ struct StationDetailView: View {
ToolbarItem(placement: .cancellationAction) {
Button("Done") { dismiss() }
}
ToolbarItem(placement: .confirmationAction) {
Button {
onToggleFavourite?()
} label: {
Image(systemName: isFavourite ? "star.fill" : "star")
}
.tint(isFavourite ? Color.yellow : nil)
.disabled(onToggleFavourite == nil)
.accessibilityLabel(
isFavourite
? String(localized: "Remove from favourites", comment: "Unstar a station from the More info sheet")
: String(localized: "Add to favourites", comment: "Star a station from the More info sheet")
)
}
}
}
}
FuelBoard/StationsView.swift
+16 -1
View File
@@ -155,6 +155,7 @@ struct StationsView: View {
topBadgeText: sortMode == .worthTheDrive ? "CHEAPEST" : "TOP",
tapAction: stationTapAction,
fuelSavings: savingsForStation(station),
fuelSavingsAmount: fuelSavingsAmount,
onToggleFavourite: { onToggleFavourite(station, selectedFuel) },
onShowDetails: { detailStation = $0 }
)
@@ -215,6 +216,18 @@ struct StationsView: View {
if ProcessInfo.processInfo.arguments.contains("-showKeySheet") {
showKey = true
}
#endif
}
.task(id: stations.count) {
#if DEBUG
// QA hook: `-showDetail` opens the More info sheet for the first
// listed station, so the sheet can be screenshotted without a
// tap. Waits for the list to arrive first.
guard ProcessInfo.processInfo.arguments.contains("-showDetail"),
detailStation == nil,
let first = stations.first else { return }
try? await Task.sleep(nanoseconds: 2_000_000_000)
detailStation = first
#endif
}
.toolbar {
@@ -302,7 +315,9 @@ struct StationsView: View {
distanceUnit: distanceUnit,
fuelSavings: savingsForStation(station),
fuelSavingsAmount: fuelSavingsAmount,
savingsBaselineStationName: savingsBaselineStationName
savingsBaselineStationName: savingsBaselineStationName,
isFavourite: favouriteIDs.contains(station.id),
onToggleFavourite: { onToggleFavourite(station, selectedFuel) }
)
}
}
FuelBoard/en.lproj/Localizable.strings
+3
View File
@@ -31,6 +31,9 @@
"More than 4p over the cheapest" = "More than 4p over the cheapest";
"Top result for the current sort" = "Top result for the current sort";
"Star a station to add it to Favourites" = "Star a station to add it to Favourites";
/* Star button in the More info sheet heading (accessibility labels) */
"Add to favourites" = "Add to favourites";
"Remove from favourites" = "Remove from favourites";
"Colours match each station's rating on the list" = "Colours match each station's rating on the list";
/* Favourites tab */
FuelBoardTests/Tests/FuelBoardSharedTests/FuelSavingsCalculationAuditTests.swift
+419
View File
@@ -0,0 +1,419 @@
import XCTest
#if SWIFT_PACKAGE
@testable import FuelBoardShared
#endif
/// Worth the Drive calculation audit.
///
/// Written against the audit brief (30 MPG imperial, £60 fill-up, baseline
/// Rontec Shelf at 171.9p, 0.4 miles). The brief's three observed results are
/// reproduced here exactly, so any future change to the formula breaks a test
/// instead of silently shifting the numbers on screen.
///
/// Deterministic journey distances only — never live MKDirections responses.
final class FuelSavingsCalculationAuditTests: XCTestCase {
private func station(_ id: String, price: Double?) -> FuelStation {
FuelStation(
id: id,
name: id,
brand: "X",
address: "",
postcode: "",
lat: 51.5,
lng: -0.1,
prices: price.map { [FuelType.e10: $0] } ?? [:],
priceUpdated: nil
)
}
/// Journeys are OUT AND BACK (the app's convention): the brief's baseline is
/// 0.4 miles away, so its journey is 0.8 miles, and "extra driving" of N
/// miles means a candidate journey of 0.8 + N.
private func journey(_ miles: Double, basis: FuelSavingsDistanceBasis = .roadRoute) -> FuelSavingsJourney {
FuelSavingsJourney(miles: miles, basis: basis)
}
private let baselineJourneyMiles = 0.8
private func briefResult(candidatePrice: Double, extraMiles: Double) throws -> FuelSavingsResult {
try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: candidatePrice,
baselineJourneyMiles: baselineJourneyMiles,
candidateJourneyMiles: baselineJourneyMiles + extraMiles
)
}
// MARK: - 1. Unit conversion
func testImperialGallonIsUsedNotTheUSGallon() {
XCTAssertEqual(FuelSavingsCalculator.imperialGallonLitres, 4.54609)
XCTAssertNotEqual(FuelSavingsCalculator.imperialGallonLitres, 3.785411784,
"a US gallon must never be used: it would understate every travel cost")
// 30 miles at 30 MPG burns exactly one imperial gallon.
XCTAssertEqual(FuelSavingsCalculator.fuelUsedLitres(distanceMiles: 30, mpg: 30), 4.54609, accuracy: 1e-12)
// 100 miles at 50 MPG.
XCTAssertEqual(FuelSavingsCalculator.fuelUsedLitres(distanceMiles: 100, mpg: 50), 9.09218, accuracy: 1e-12)
// Zero distance burns nothing, and the relationship is linear in distance.
XCTAssertEqual(FuelSavingsCalculator.fuelUsedLitres(distanceMiles: 0, mpg: 30), 0, accuracy: 1e-12)
XCTAssertEqual(FuelSavingsCalculator.fuelUsedLitres(distanceMiles: 60, mpg: 30),
2 * FuelSavingsCalculator.fuelUsedLitres(distanceMiles: 30, mpg: 30),
accuracy: 1e-12)
}
func testMileAndKilometreFactorsAreTheExactOnes() {
XCTAssertEqual(FuelSavingsCalculator.kilometresPerMile, 1.609344)
XCTAssertEqual(FuelSavingsCalculator.metresPerMile, 1609.344)
XCTAssertEqual(FuelSavingsCalculator.metresPerMile,
FuelSavingsCalculator.kilometresPerMile * 1000,
accuracy: 1e-9,
"the metre and kilometre factors must describe the same mile")
}
func testDistanceLabelUsesTheSameConversionAsTheModel() {
// One mile, shown in kilometres, goes through the single factor.
XCTAssertEqual(
FuelSavingsFormat.distance(1, unit: .kilometers),
DistanceUnit.kilometers.format(FuelSavingsCalculator.kilometresPerMile)
)
XCTAssertEqual(FuelSavingsFormat.distance(1, unit: .miles), DistanceUnit.miles.format(1.609344))
}
// MARK: - 2/4. The three stations from the brief
func testBriefCaseTescoBradfordIsMarginallyWorseOff() throws {
let result = try briefResult(candidatePrice: 170.9, extraMiles: 2.0)
XCTAssertEqual(result.fillLitres, 34.904014, accuracy: 1e-6)
XCTAssertEqual(result.grossSavingGBP, 0.349040, accuracy: 1e-6, "1p/litre cheaper on a 34.90 L fill")
XCTAssertEqual(result.extraDistanceMiles, 2.0, accuracy: 1e-9)
XCTAssertEqual(result.extraDrivingCostGBP, 0.517951, accuracy: 1e-6)
XCTAssertEqual(result.netSavingGBP, -0.168911, accuracy: 1e-6)
XCTAssertEqual(result.status, .notWorthTheDrive)
XCTAssertEqual(result.headline(), "£0.17 worse off after travel")
}
/// The brief recorded "£0.18 worse off" for this row against a displayed
/// "2.0 miles" of extra driving; the brief also warns that the displayed
/// mileage is rounded. This pins that explanation instead of treating it as
/// a calculation bug: at an extra distance the caption still shows as
/// "2.0 mi" (2.00-2.05), the headline reads £0.17-£0.18, and the difference
/// is entirely the rounding of the distance, not of the money.
func testTheReportedEighteenPenceIsRoundedExtraDistanceNotARoundingBug() throws {
XCTAssertEqual(try briefResult(candidatePrice: 170.9, extraMiles: 2.00).headline(),
"£0.17 worse off after travel")
XCTAssertEqual(try briefResult(candidatePrice: 170.9, extraMiles: 2.05).headline(),
"£0.18 worse off after travel")
// 2.05 mi shows as "2.0 mi" at one decimal place — the same caption.
XCTAssertEqual(FuelSavingsFormat.extraTravelLabel(extraDistanceMiles: 2.05, unit: .miles),
"2.0 mi more driving than closest")
XCTAssertEqual(FuelSavingsFormat.extraTravelLabel(extraDistanceMiles: 2.00, unit: .miles),
"2.0 mi more driving than closest")
}
func testBriefCaseMFGHareAndHoundsIsWorseOff() throws {
let result = try briefResult(candidatePrice: 172.9, extraMiles: 2.8)
XCTAssertEqual(result.fillLitres, 34.904014, accuracy: 1e-6)
XCTAssertEqual(result.grossSavingGBP, -0.349040, accuracy: 1e-6, "1p/litre dearer costs 34.90 L × 1p")
XCTAssertEqual(result.extraDistanceMiles, 2.8, accuracy: 1e-9)
XCTAssertEqual(result.extraDrivingCostGBP, 0.733618, accuracy: 1e-6)
XCTAssertEqual(result.netSavingGBP, -1.082658, accuracy: 1e-6)
XCTAssertEqual(result.status, .notWorthTheDrive)
XCTAssertEqual(result.headline(), "£1.08 worse off after travel")
}
func testBriefCasePGGNapoleonSamePumpPriceIsTravelCostOnly() throws {
let result = try briefResult(candidatePrice: 171.9, extraMiles: 2.8)
XCTAssertEqual(result.grossSavingGBP, 0, accuracy: 1e-9, "same pump price saves nothing at the pump")
XCTAssertEqual(result.extraDrivingCostGBP, 0.729375, accuracy: 1e-6)
XCTAssertEqual(result.netSavingGBP, -0.729375, accuracy: 1e-6,
"with no price difference the whole result is the extra driving")
XCTAssertEqual(result.status, .notWorthTheDrive)
XCTAssertEqual(result.headline(), "£0.73 worse off after travel")
}
// MARK: - 5/6. Classification, tolerance and rounding
func testSamePriceAndSameDistanceIsBreakEven() throws {
let result = try briefResult(candidatePrice: 171.9, extraMiles: 0)
XCTAssertEqual(result.grossSavingGBP, 0, accuracy: 1e-9)
XCTAssertEqual(result.extraDrivingCostGBP, 0, accuracy: 1e-9)
XCTAssertEqual(result.netSavingGBP, 0, accuracy: 1e-9)
XCTAssertEqual(result.status, .breakEven)
XCTAssertEqual(result.headline(), "Break even")
}
func testSmallSavingInsideTheToleranceIsBreakEvenNotPennies() throws {
// 171.9p vs 170.9p over a 1.23 mi delta: net +£0.0305.
let result = try briefResult(candidatePrice: 170.9, extraMiles: 1.23)
XCTAssertEqual(result.netSavingGBP, 0.030500, accuracy: 1e-6)
XCTAssertEqual(result.status, .breakEven, "±5p reads as break even rather than a meaningless £0.03")
XCTAssertEqual(result.headline(), "Break even")
}
func testBreakEvenToleranceDecidesTheClassificationAtTheBoundary() throws {
let net = -0.168911
// A tolerance wider than the loss → break even; narrower → worse off.
let lenient = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 170.9,
baselineJourneyMiles: baselineJourneyMiles,
candidateJourneyMiles: baselineJourneyMiles + 2.0,
breakEvenToleranceGBP: 0.17
)
XCTAssertEqual(lenient.netSavingGBP, net, accuracy: 1e-6)
XCTAssertEqual(lenient.status, .breakEven)
let strict = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 170.9,
baselineJourneyMiles: baselineJourneyMiles,
candidateJourneyMiles: baselineJourneyMiles + 2.0,
breakEvenToleranceGBP: 0.16
)
XCTAssertEqual(strict.status, .notWorthTheDrive)
}
func testMoneyIsRoundedOnlyForDisplay() throws {
// Full precision retained internally…
let result = try briefResult(candidatePrice: 172.9, extraMiles: 2.8)
XCTAssertEqual(result.netSavingGBP, -1.082658, accuracy: 1e-6)
XCTAssertNotEqual(result.netSavingGBP, -1.08, "the stored value must not be pre-rounded")
// …and rounded to two places only when shown.
XCTAssertEqual(FuelSavingsFormat.money(1.082658), "£1.08")
XCTAssertEqual(FuelSavingsFormat.money(0.729375), "£0.73")
XCTAssertEqual(FuelSavingsFormat.money(0.1749), "£0.17")
XCTAssertEqual(FuelSavingsFormat.money(0.176), "£0.18")
XCTAssertEqual(FuelSavingsFormat.money(0), "£0.00")
}
func testSortingUsesTheUnroundedNetSoRoundedTiesStillOrderCorrectly() {
// Two rows that both DISPLAY "£0.18 worse off" but differ in the raw
// figure: the sort must use the raw value, never the shown one.
func ranked(_ id: String, net: Double) -> FuelSavingsRankedStation {
FuelSavingsRankedStation(
stationID: id,
result: .available(FuelSavingsResult(
fillLitres: 34.9,
grossSavingGBP: 0,
extraDrivingCostGBP: abs(net),
extraDistanceMiles: 2.0,
netSavingGBP: net,
status: .notWorthTheDrive
)),
distanceMiles: 2.8,
pricePencePerLitre: 171.9
)
}
let worse = ranked("worse", net: -0.1751)
let lessWorse = ranked("less-worse", net: -0.1749)
XCTAssertEqual(FuelSavingsFormat.money(abs(worse.result.result!.netSavingGBP)), "£0.18")
XCTAssertEqual(FuelSavingsFormat.money(abs(lessWorse.result.result!.netSavingGBP)), "£0.17")
let sorted = FuelSavingsCalculator.sortedForWorthTheDrive([worse, lessWorse])
XCTAssertEqual(sorted.first?.stationID, "less-worse",
"the smaller loss must rank first even when the money rounds to the same figure")
}
// MARK: - 3. Distances and travel cost
func testCheaperFuelFurtherAwayCanStillBeWorthTheDrive() throws {
// 145.9p nearby vs 138.9p five miles further out, £40 fill, 45 MPG.
let result = try FuelSavingsCalculator.calculate(
mpg: 45,
amount: FuelSavingsFillAmount(value: 40, unit: .pounds),
baselinePricePencePerLitre: 145.9,
candidatePricePencePerLitre: 138.9,
baselineJourneyMiles: 2.0,
candidateJourneyMiles: 7.0
)
XCTAssertEqual(result.fillLitres, 27.416038, accuracy: 1e-6)
XCTAssertEqual(result.grossSavingGBP, 1.919123, accuracy: 1e-6)
XCTAssertEqual(result.extraDrivingCostGBP, 0.701613, accuracy: 1e-6)
XCTAssertEqual(result.netSavingGBP, 1.217509, accuracy: 1e-6)
XCTAssertEqual(result.status, .worthTheDrive)
XCTAssertEqual(result.headline(), "Save £1.22 after travel")
}
func testNearerCandidateIsNeverChargedExtraTravel() throws {
// The baseline is the nearest priced station, so this should not happen
// in the app — but the clamp must hold if it ever does.
let result = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 169.9,
baselineJourneyMiles: 2.0,
candidateJourneyMiles: 1.0
)
XCTAssertEqual(result.extraDistanceMiles, 0, "a shorter journey is never a negative extra distance")
XCTAssertEqual(result.extraDrivingCostGBP, 0, accuracy: 1e-12)
XCTAssertEqual(result.netSavingGBP, result.grossSavingGBP, accuracy: 1e-12)
}
func testDifferentMPGValuesScaleOnlyTheTravelCost() throws {
let sixty = try FuelSavingsCalculator.calculate(
mpg: 60,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 172.9,
baselineJourneyMiles: 0.8,
candidateJourneyMiles: 3.6
)
XCTAssertEqual(sixty.grossSavingGBP, -0.349040, accuracy: 1e-6, "MPG must not touch the pump saving")
XCTAssertEqual(sixty.extraDrivingCostGBP, 0.366809, accuracy: 1e-6)
XCTAssertEqual(sixty.netSavingGBP, -0.715849, accuracy: 1e-6)
let fortyFive = try FuelSavingsCalculator.calculate(
mpg: 45,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 172.9,
baselineJourneyMiles: 0.8,
candidateJourneyMiles: 3.6
)
XCTAssertEqual(fortyFive.extraDrivingCostGBP, 0.489078, accuracy: 1e-6)
XCTAssertEqual(fortyFive.netSavingGBP, -0.838119, accuracy: 1e-6)
}
func testDifferentFillBudgetsScaleOnlyThePumpSaving() throws {
let forty = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 40, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 172.9,
baselineJourneyMiles: 0.8,
candidateJourneyMiles: 3.6
)
XCTAssertEqual(forty.fillLitres, 23.269343, accuracy: 1e-6, "£40 buys 23.27 L at 171.9p")
XCTAssertEqual(forty.grossSavingGBP, -0.232693, accuracy: 1e-6)
XCTAssertEqual(forty.extraDrivingCostGBP, 0.733618, accuracy: 1e-6, "the journey cost is budget-independent")
XCTAssertEqual(forty.netSavingGBP, -0.966311, accuracy: 1e-6)
let ninety = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 90, unit: .pounds),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 172.9,
baselineJourneyMiles: 0.8,
candidateJourneyMiles: 3.6
)
XCTAssertEqual(ninety.fillLitres, 52.356021, accuracy: 1e-6)
XCTAssertEqual(ninety.grossSavingGBP, -0.523560, accuracy: 1e-6)
XCTAssertEqual(ninety.netSavingGBP, -1.257178, accuracy: 1e-6)
}
func testFillUpInLitresIsFixedRegardlessOfPrice() throws {
// 40 L is 40 L: no baseline price is involved in the quantity.
let result = try FuelSavingsCalculator.calculate(
mpg: 30,
amount: FuelSavingsFillAmount(value: 40, unit: .litres),
baselinePricePencePerLitre: 171.9,
candidatePricePencePerLitre: 165.9,
baselineJourneyMiles: 0.8,
candidateJourneyMiles: 3.6
)
XCTAssertEqual(result.fillLitres, 40, accuracy: 1e-9)
XCTAssertEqual(result.grossSavingGBP, 40 * 0.06, accuracy: 1e-9)
}
// MARK: - 7. Failures never invent a saving
func testUnavailableRouteProducesNoSavingAtAll() {
let baseline = station("baseline", price: 171.9)
let candidate = station("candidate", price: 170.9)
let settings = FuelSavingsSettings(
enabled: true,
mpg: 30,
preferredAmount: FuelSavingsFillAmount(value: 60, unit: .pounds)
)
let noRoute = FuelSavingsEstimator.availability(
station: candidate,
fuel: .e10,
baseline: baseline,
settings: settings,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
journey: nil,
baselineJourney: journey(0.8)
)
XCTAssertEqual(noRoute, .unavailable("Distance unavailable"))
let noBaselineRoute = FuelSavingsEstimator.availability(
station: candidate,
fuel: .e10,
baseline: baseline,
settings: settings,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
journey: journey(2.8),
baselineJourney: nil
)
XCTAssertEqual(noBaselineRoute, .unavailable("No comparison station"))
// With both legs present it produces the saving — no silent zero.
let both = FuelSavingsEstimator.availability(
station: candidate,
fuel: .e10,
baseline: baseline,
settings: settings,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
journey: journey(2.8),
baselineJourney: journey(0.8)
)
XCTAssertEqual(both?.result?.netSavingGBP ?? 0, -0.168911, accuracy: 1e-6)
}
func testMixedRouteBasisIsReportedAsAnEstimate() {
let baseline = station("baseline", price: 171.9)
let candidate = station("candidate", price: 170.9)
let settings = FuelSavingsSettings(
enabled: true,
mpg: 30,
preferredAmount: FuelSavingsFillAmount(value: 60, unit: .pounds)
)
let mixed = FuelSavingsEstimator.availability(
station: candidate,
fuel: .e10,
baseline: baseline,
settings: settings,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
journey: journey(2.8, basis: .straightLine),
baselineJourney: journey(0.8, basis: .roadRoute)
)
XCTAssertEqual(mixed?.result?.distanceBasis, .straightLine,
"one unmeasured leg makes the whole estimate an estimate")
let headline = mixed?.result?.headline(compact: true) ?? ""
XCTAssertTrue(headline.hasSuffix(" (est.)"), "an estimate must be marked as one, got \(headline)")
}
func testBaselineStationIsLabelledClosestStationNotBreakEven() {
let baseline = station("baseline", price: 171.9)
let settings = FuelSavingsSettings(
enabled: true,
mpg: 30,
preferredAmount: FuelSavingsFillAmount(value: 60, unit: .pounds)
)
let result = FuelSavingsEstimator.availability(
station: baseline,
fuel: .e10,
baseline: baseline,
settings: settings,
amount: FuelSavingsFillAmount(value: 60, unit: .pounds),
journey: journey(0.8),
baselineJourney: journey(0.8)
)?.result
XCTAssertEqual(result?.status, .baseline)
XCTAssertEqual(result?.netSavingGBP, 0)
XCTAssertEqual(result?.headline(), "Closest station")
}
}
FuelBoardTests/Tests/FuelBoardSharedTests/FuelSavingsEstimateTests.swift
+58
View File
@@ -374,4 +374,62 @@ final class FuelSavingsEstimateTests: XCTestCase {
"net saving decides the order, not the pump price")
XCTAssertEqual(ranked.last?.id, "cheap-but-far")
}
// MARK: Row copy
/// The row's extra-driving caption must follow the DISPLAY unit: the stored
/// figure is always miles, and converting by the current unit instead would
/// leave a km user's figure unlabelled and 1.6× too large.
func testExtraTravelLabelFollowsTheDisplayUnit() {
XCTAssertEqual(
FuelSavingsFormat.extraTravelLabel(extraDistanceMiles: 19.9, unit: .miles),
"19.9 mi more driving than closest"
)
XCTAssertEqual(
FuelSavingsFormat.extraTravelLabel(extraDistanceMiles: 19.9, unit: .kilometers),
"32.0 km more driving than closest"
)
XCTAssertNil(FuelSavingsFormat.extraTravelLabel(extraDistanceMiles: 0, unit: .miles),
"the baseline row has no extra travel to report")
// The same conversion backs the detail sheet's extra-distance figure,
// which used to be hardcoded miles ("%.1f miles") for km users too.
XCTAssertEqual(FuelSavingsFormat.distance(19.9, unit: .miles), "19.9 mi")
XCTAssertEqual(FuelSavingsFormat.distance(19.9, unit: .kilometers), "32.0 km")
}
/// The baseline capsule has to say what it IS: it previously repeated the
/// status word above it ("Closest station" twice) and never explained that
/// the savings are measured against it.
func testCapsuleHeadlineMarksTheBaselineAndKeepsTheEstimateMarker() {
let baseline = FuelSavingsResult(
fillLitres: 30,
grossSavingGBP: 0,
extraDrivingCostGBP: 0,
extraDistanceMiles: 0,
netSavingGBP: 0,
status: .baseline
)
XCTAssertEqual(baseline.capsuleHeadline(), "Closest station · your baseline")
let saving = FuelSavingsResult(
fillLitres: 30,
grossSavingGBP: 2.40,
extraDrivingCostGBP: 1.40,
extraDistanceMiles: 5.2,
netSavingGBP: 1.00,
status: .worthTheDrive,
distanceBasis: .straightLine
)
XCTAssertEqual(saving.capsuleHeadline(), "Save £1.00 after travel (est.)")
let worse = FuelSavingsResult(
fillLitres: 30,
grossSavingGBP: 1.40,
extraDrivingCostGBP: 1.70,
extraDistanceMiles: 6.7,
netSavingGBP: -0.31,
status: .notWorthTheDrive
)
XCTAssertEqual(worse.capsuleHeadline(), "£0.31 worse off after travel")
}
}
Shared/FuelSavings.swift
+39
View File
@@ -100,6 +100,25 @@ enum FuelSavingsFormat {
static func money(_ value: Double) -> String {
String(format: "£%.2f", value)
}
/// A distance stored in MILES, formatted in the display unit. The figures
/// behind an estimate are stored in miles whatever the user's unit, so this
/// is the one place that conversion lives.
static func distance(_ miles: Double, unit: DistanceUnit) -> String {
// Convert miles→km FIRST, then let the unit format it. `unit.toKM` would
// convert by the CURRENT unit instead, leaving a km user's figure
// unlabelled and 1.6× too large.
unit.format(miles * FuelSavingsCalculator.kilometresPerMile)
}
/// Row label for the extra driving a saving has to beat. The stored figure is
/// always MILES while the row's distance line is one-way, so the wording says
/// "more driving": the extra is an out-and-back figure and can legitimately
/// exceed the one-way distance, which read as a contradiction before.
static func extraTravelLabel(extraDistanceMiles: Double, unit: DistanceUnit) -> String? {
guard extraDistanceMiles > 0.05 else { return nil }
return "\(distance(extraDistanceMiles, unit: unit)) more driving than closest"
}
}
extension FuelSavingsResult {
@@ -140,6 +159,15 @@ extension FuelSavingsResult {
return "\(FuelSavingsFormat.money(abs(netSavingGBP))) worse off after travel\(estimate)"
}
}
/// Row capsule copy: the headline, plus what the baseline row IS. Without the
/// suffix the baseline capsule just repeated the status word above it
/// ("Closest station" twice) and said nothing about the saving being measured
/// against it.
func capsuleHeadline() -> String {
let headline = headline(compact: true)
return status == .baseline ? "\(headline) · your baseline" : headline
}
}
/// One station's journey distance, plus how it was obtained.
@@ -173,7 +201,18 @@ enum FuelSavingsError: Error, Equatable {
}
enum FuelSavingsCalculator {
/// 1 UK (imperial) gallon. Must never be the US gallon (3.785411784 L):
/// UK pumps are priced per litre and drivers quote UK MPG, so a US gallon
/// would understate every travel cost by 17%.
static let imperialGallonLitres = 4.54609
/// Exact mile↔kilometre factors (1 mile = 1.609344 km). Every figure the
/// savings maths keeps is in MILES, and every displayed or fallback
/// distance converts through these, so one quantity is never converted with
/// two different constants. The audit found 1.60934, 1609.34 and 0.621371
/// mixed in the same path — a ~2 parts-per-million difference, immaterial to
/// the money, but three constants where there should be one.
static let kilometresPerMile = 1.609344
static let metresPerMile = 1609.344
static let breakEvenToleranceGBP = 0.05
static let minimumMPG: Double = 5
static let maximumMPG: Double = 200