Share
Embed
Slide 1
Slide 1 text
Snapshot Testing in Practice:
Predictable and Reliable SwiftUI Views
Felipe Espinoza - October 2026
Slide 2
Slide 2 text
🇨🇱🇳🇴
10 years developing for apple platforms
Lead developer for the iOS app at SATS
Youtuber
Slide 3
Slide 3 text
No content
Slide 4
Slide 4 text
No content
Slide 5
Slide 5 text
No content
Slide 6
Slide 6 text
No content
Slide 7
Slide 7 text
No content
Slide 8
Slide 8 text
No content
Slide 9
Slide 9 text
🇳🇴 🇸🇪 🇩🇰 🇫🇮
Slide 10
Slide 10 text
~620000
Unique users per month iOS app
Slide 11
Slide 11 text
Snapshot Testing to improve the craft of your UI code
and extra benefits of working with them
Slide 12
Slide 12 text
Making code easier to test
Reduce coupling
Better code
Easier to reason about
More maintainable
Slide 13
Slide 13 text
Agenda
What’s Snapshot Testing?
How to use it?
How to control data?
Practical problems to solve
Slide 14
Slide 14 text
Agenda
What’s Snapshot Testing?
How to use it?
How to control data?
Practical problems to solve
Slide 15
Slide 15 text
Unit test for your UI Code
Slide 16
Slide 16 text
􀏅
Snapshot Test
Test File
Rendered UI
Reference Image
Slide 17
Slide 17 text
import SwiftUI
import SnapshotTesting
import Testing
@testable import NordicGym
@MainActor
@Suite
struct `Home Screen Snapshots` {
@Test func `sample content`() async throws {
let view = NavigationStack {
HomeScreen()
}
.environment(\.networkingClient, .test())
?
assertSnapshot(of: view, as: .image)
}
}
Rendered UI
Reference Image
Slide 18
Slide 18 text
􀆄
import SwiftUI
import SnapshotTesting
import Testing
@testable import NordicGym
@MainActor
@Suite
struct `Home Screen Snapshots` {
@Test func `sample content`() async throws {
let view = NavigationStack {
HomeScreen()
}
.environment(\.networkingClient, .test())
assertSnapshot(of: view, as: .image)
}
}
Reference Image
Slide 19
Slide 19 text
􀆅
import SwiftUI
import SnapshotTesting
import Testing
@testable import NordicGym
@MainActor
@Suite
struct `Home Screen Snapshots` {
@Test func `sample content`() async throws {
let view = NavigationStack {
HomeScreen()
}
.environment(\.networkingClient, .test())
assertSnapshot(of: view, as: .image)
}
}
Rendered UI
Reference Image
Slide 20
Slide 20 text
Device Type (+ Model)
iPhone 18 Pro
iPhone Air
iPad 11 Inch 2026
Orientation
Portrait
Split
1/3
Half
Interface Style
Light
Dark
Localization
English
German
Norwegian
Region
Norway
Germany
United States
Dynamic type
Small
iPad Air 2025
Landscape
2/3
Large
Many other accessibility settings…
Full
Extra Large
Spanish
Chile
Accessibility1
Accessibility5
…
…
Slide 21
Slide 21 text
Device Type (+ Model)
iPhone 18 Pro
iPhone Air
iPad 11 Inch 2026
Orientation
Portrait
Split
1/3
Half
Interface Style
Light
Dark
Localization
English
German
Norwegian
Region
Norway
Germany
United States
Dynamic type
Small
iPad Air 2025
Landscape
2/3
Large
Many other accessibility settings…
Full
Extra Large
Spanish
Chile
Accessibility1
Accessibility5
…
…
Slide 22
Slide 22 text
Device Type (+ Model)
iPhone 18 Pro
iPhone Air
iPad 11 Inch 2026
Orientation
Portrait
Split
1/3
Half
Interface Style
Light
Dark
Localization
English
German
Norwegian
Region
Norway
Germany
United States
Dynamic type
Small
iPad Air 2025
Landscape
2/3
Large
Many other accessibility settings…
Full
Extra Large
Spanish
Chile
Accessibility1
Accessibility5
…
…
Slide 23
Slide 23 text
Device Type (+ Model)
iPhone 18 Pro
iPhone Air
iPad 11 Inch 2026
Orientation
Portrait
Split
1/3
Half
Interface Style
Light
Dark
Localization
English
German
Norwegian
Region
Norway
Germany
United States
Dynamic type
Small
iPad Air 2025
Landscape
2/3
Large
Many other accessibility settings…
Full
Extra Large
Spanish
Chile
Accessibility1
Accessibility5
…
…
Slide 24
Slide 24 text
Combination Count
Slide 25
Slide 25 text
No content
Slide 26
Slide 26 text
What about Xcode Previews?
You need to actively run them
Snapshot ensure your UI keeps working well
Making your UI easier to test also improves previews
Slide 27
Slide 27 text
No content
Slide 28
Slide 28 text
No content
Slide 29
Slide 29 text
No content
Slide 30
Slide 30 text
Agenda
What’s Snapshot Testing?
How to use it?
How to control data?
Practical problems to solve
Slide 31
Slide 31 text
No content
Slide 32
Slide 32 text
DEMO
First snapshot testing
Slide 33
Slide 33 text
No content
Slide 34
Slide 34 text
No content
Slide 35
Slide 35 text
No content
Slide 36
Slide 36 text
No content
Slide 37
Slide 37 text
No content
Slide 38
Slide 38 text
No content
Slide 39
Slide 39 text
92 snapshot-test suites
194 test methods inside those suites
202 expectSnapshot call sites
91 snapshot source les/directories
fi
858 PNG reference images
Slide 40
Slide 40 text
Agenda
What’s Snapshot Testing?
How to use it?
How to control data?
Practical problems to solve
Slide 41
Slide 41 text
struct HomeScreen: View {
@State var content: BasicLoadingState<[HomeModuleViewData]> = .idle
@Environment(\.networkingClient.fetchHomeContent) var fetchHomeContent
var body: some View {
BasicStateView(state: $content) { viewData in
HomeView(modules: viewData)
} fetchData: {
let dto = try await fetchHomeContent()
return dto.map { HomeModuleViewData(dto: $0) }
}
}
}
Slide 42
Slide 42 text
No content
Slide 43
Slide 43 text
No content
Slide 44
Slide 44 text
No content
Slide 45
Slide 45 text
{
"items": [
{
"type": "upcomingClasses",
"content": [
{
"id": "love2dance-20260911-1730",
"name": "Love2Dance",
"instructorName": "Eva",
"location": "Ringnes Park",
"dateTime": "2026-09-11T17:30:00+02:00",
"durationInMinutes": 60,
"bookingState": "booked",
"availableSpots": 3,
"imageURL": "https://images.pexels.com/photos/5936039/pexels-photo-5936039.jpeg?auto=compress&cs=tinysrgb&w=900"
},
{
"id": "rowing-20260912-1830",
"name": "Rowing",
"instructorName": "Erling",
"location": "Ringnes Park",
"dateTime": "2026-09-12T18:30:00+02:00",
"durationInMinutes": 30,
"bookingState": "booked",
"availableSpots": 8,
"imageURL": "https://images.pexels.com/photos/4162486/pexels-photo-4162486.jpeg?auto=compress&cs=tinysrgb&w=900"
},
{
"id": "yoga-flow-20260913-1000",
"name": "Yoga Flow",
"instructorName": "Ingrid",
"location": "Majorstuen",
"dateTime": "2026-09-13T10:00:00+02:00",
"durationInMinutes": 60,
"bookingState": "bookedOnWaitingList",
"availableSpots": 0,
"imageURL": "https://images.pexels.com/photos/4587342/pexels-photo-4587342.jpeg?auto=compress&cs=tinysrgb&w=900"
}
]
},
{
"type": "friendActivity",
Slide 46
Slide 46 text
"instructorName": "Jonas",
"location": "Nydalen",
"dateTime": "2026-09-12T12:00:00+02:00",
"durationInMinutes": 30,
"bookingState": "notBooked",
"availableSpots": 1,
"imageURL": "https://images.pexels.com/photos/3757943/pexels-photo-3757943.jpeg?auto=compress&cs=tinysrgb&w=900"
}
},
{
"friend": {
"id": "member-mikkel",
"firstName": "Mikkel",
"lastName": "Solberg",
"profilePicture": "https://randomuser.me/api/portraits/men/75.jpg"
},
"groupClass": {
"id": "dance-energy-20260913-1600",
"name": "Dance Energy",
"instructorName": "Eva",
"location": "Ringnes Park",
"dateTime": "2026-09-13T16:00:00+02:00",
"durationInMinutes": 50,
"bookingState": "notBookedOnWaitingList",
"availableSpots": 0,
"imageURL": "https://images.pexels.com/photos/5936039/pexels-photo-5936039.jpeg?auto=compress&cs=tinysrgb&w=900"
}
}
]
},
{
"type": "featuredContent",
"content": {
"id": "88B995ED-C598-4622-AD58-0BD07B508471",
"title": "What are your objectives?",
"message": "Build strength, find your rhythm, or make more time for yourself. Explore classes that fit your goals and plan your next workout with a
friend.",
"imageURL": "https://images.pexels.com/photos/4587371/pexels-photo-4587371.jpeg?auto=compress&cs=tinysrgb&w=900"
}
}
]
}
Slide 47
Slide 47 text
struct UpcomingClassesCard: View {
let sections: [UpcomingClassesSectionViewData]
var body: some View {
VStack(alignment: .leading, spacing: .spacingL) {
ForEach(sections) { section in
VStack(alignment: .leading) {
// Section Title
}
}
}
}
VStack(alignment: .leading, spacing: .spacingM) {
ForEach(section.classes) { row in
GroupClassRow(viewData: row)
}
}
}
.cardStyle()
Slide 48
Slide 48 text
struct GroupClassRow: View {
let viewData: GroupClassRowViewData
var body: some View {
NavigationLink(destination: { GroupClassScreen(id: viewData.id) }) {
HStack(spacing: .spacingM) {
Spacer(minLength: 4)
HStack(alignment: .top, spacing: .spacingM) {
VStack(alignment: .leading) {
Text(viewData.time.formatted(date: .omitted, time: .shortened))
Text(viewData.duration)
.foregroundStyle(.secondary)
.font(.footnote)
}
VStack(alignment: .leading) {
Text(viewData.className)
Text("w/ \(viewData.instructorName)")
.foregroundStyle(.secondary)
Text(viewData.location)
.foregroundStyle(.secondary)
Text(viewData.bookingState.message)
.foregroundStyle(viewData.bookingState.foregroundColor)
}
.frame(maxWidth: .infinity, alignment: .leading)
}
Image(systemName: viewData.bookingState.imageName)
Slide 49
Slide 49 text
ViewData
Slide 50
Slide 50 text
ViewData
Just the "right amount" of data for a view
The data in the "right" format*
Slide 51
Slide 51 text
{
"id": "dance-energy-20260913-1600",
"gym": {
"id": "ringnes-park",
"name": "Ringnes Park"
},
"room": "Dance Studio",
"instructor": {
"id": "eva-larsen",
"firstName": "Eva",
"lastName": "Larsen"
},
"startTime": "2026-09-13T16:00:00+02:00",
"durationInMinutes": 50,
"bookingState": "notBookedOnWaitingList",
"availableSpots": 0,
"capacity": 30,
"friendsAttending": [
{
"member": {
"id": "member-mikkel",
"firstName": "Mikkel",
"lastName": "Solberg",
"profilePicture": "https://randomuser.me/api/portraits/men/75.jpg"
},
"bookingState": "booked"
}
],
"similarClasses": [
{
"id": "love2dance-20260911-1730",
"name": "Love2Dance",
"instructorName": "Eva",
"location": "Ringnes Park",
"dateTime": "2026-09-11T17:30:00+02:00",
"durationInMinutes": 60,
"bookingState": "booked",
"availableSpots": 3,
"imageURL": "https://images.pexels.com/photos/5936039/pexels-photo-5936039.jpeg?auto=compress&cs=tinysrgb&w=900"
}
],
"name": "Dance Energy",
"description": "Move to upbeat music in an energetic dance workout. Follow Eva through easy-to-learn combinations that build coordination and get your heart pumping.",
"imageURL": "https://images.pexels.com/photos/5936039/pexels-photo-5936039.jpeg?auto=compress&cs=tinysrgb&w=900",
"intensity": "high"
}
Slide 52
Slide 52 text
struct GroupClass: Decodable {
let id: GroupClassID
let gym: Gym
let room: String?
let instructor: Instructor
let startTime: Date
let durationInMinutes: Int
let bookingState: BookingState
let availableSpots: Int
let capacity: Int
let friendsAttending: [FriendAttending]
let similarClasses: [UpcomingGroupClass]
let name: String
let description: String
let imageURL: URL?
let intensity: Intensity
enum Intensity: String, Codable {
case low
case medium
case high
}
}
Slide 53
Slide 53 text
struct GroupClassRowViewData: Identifiable, Equatable {
let id: GroupClassID
let className: String
let instructorName: String
let location: String
let time: Date
let duration: String
let bookingState: BookingStateViewData
}
Slide 54
Slide 54 text
extension GroupClassRowViewData {
init(dto: GroupClass) {
self.init(
id: dto.id,
className: dto.name,
instructorName: PersonNameComponents(
givenName: dto.instructor.firstName,
familyName: dto.instructor.lastName
).formatted(),
location: dto.gym.name,
time: dto.startTime,
duration: dto.durationInMinutes.formatted() + " min",
bookingState: .init(
dto: dto.bookingState,
availableSpots: dto.availableSpots
)
)
}
}
DTO
ViewData
Slide 55
Slide 55 text
extension GroupClassRowViewData {
static func previewValue(
id: GroupClassID = .previewValue(),
className: String = "Love2Dance",
instructorName: String = "Eva",
location: String = "Ringnes Park",
time: Date = Date(),
duration: String = "60 min",
bookingState: BookingStateViewData = .previewValue()
) -> Self {
.init(
id: id,
className: className,
instructorName: instructorName,
location: location,
time: time,
duration: duration,
bookingState: bookingState
)
}
}
Slide 56
Slide 56 text
No content
Slide 57
Slide 57 text
Component states?
Some data: best case
Empty state
Long names
Too many items
Slide 58
Slide 58 text
No content
Slide 59
Slide 59 text
Empty State
Long Names
Slide 60
Slide 60 text
View Context
Logic of Data
Slide 61
Slide 61 text
Making code easier to test
Reduce coupling
Better code
Easier to reason about
More maintainable
Slide 62
Slide 62 text
Agenda
What’s Snapshot Testing?
How to use it?
How to control data?
Practical problems to solve
Slide 63
Slide 63 text
view = f(state)
Slide 64
Slide 64 text
Practical problems to solve
Setting up Xcode Cloud
Controlling time zones
Controlling image loading
fl
The " ashing" problem
Slide 65
Slide 65 text
No content
Slide 66
Slide 66 text
The test runner doesn’t have access to the Source Code, then it
cannot see the reference images
Slide 67
Slide 67 text
No content
Slide 68
Slide 68 text
Practical problems to solve
Setting up Xcode Cloud
Controlling time zones
Controlling image loading
fl
The " ashing" problem
Slide 69
Slide 69 text
No content
Slide 70
Slide 70 text
􀆄
(GTM+1) Europe/Oslo
(GTM+7) Asia/Tonsk
Slide 71
Slide 71 text
struct GroupClassRowViewData: Identifiable, Equatable {
let id: GroupClassID
let className: String
let instructorName: String
let location: String
let time: Date
let duration: Int
let bookingState: BookingStateViewData
}
Slide 72
Slide 72 text
struct GroupClassRow: View {
let viewData: GroupClassRowViewData
var body: some View {
NavigationLink(destination: { GroupClassScreen(id: viewData.id) }) {
HStack(spacing: .spacingM) {
Spacer(minLength: 4)
HStack(alignment: .top, spacing: .spacingM) {
VStack(alignment: .leading) {
Text(viewData.time.formatted(date: .omitted, time: .shortened))
//...
Slide 73
Slide 73 text
struct GroupClassRowViewData: Identifiable, Equatable {
let id: GroupClassID
let className: String
let instructorName: String
let location: String
let time: String
let duration: String
let bookingState: BookingStateViewData
}
Slide 74
Slide 74 text
extension GroupClassRowViewData {
init(dto: UpcomingGroupClass) {
self.init(
id: dto.id,
className: dto.name,
instructorName: dto.instructorName,
location: dto.location,
time: dto.dateTime.formatted(date: .omitted, time: .shortened),
duration: dto.durationInMinutes.formatted() + " min",
bookingState: .init(
dto: dto.bookingState,
availableSpots: dto.availableSpots
)
)
}
}
Slide 75
Slide 75 text
@Test(arguments: SnapshotVariant.defaultVariants(checkAccessibility: true))
func `home content - controlling the time zones`(variant: SnapshotVariant) async throws {
let view = NavigationStack { HomeScreen() }
.environment(
\.dataClient.fetchHomeContent,
{
[
.upcomingWorkouts([
.previewValue(
title: "Tomorrow",
classes: [.previewValue(time: "17:30")]
),
.previewValue(
title: "Friday",
classes: [.previewValue(className: "Rowing", time: "18:30")]
),
.previewValue(
title: "Saturday",
classes: [.previewValue(className: "Yoga Flow", time: "10:00")]
),
])
]
}
)
expectSnapshot(of: view, on: variant)
}
Slide 76
Slide 76 text
Practical problems to solve
Setting up Xcode Cloud
Controlling time zones
Controlling image loading
fl
The " ashing" problem
Slide 77
Slide 77 text
No content
Slide 78
Slide 78 text
No content
Slide 79
Slide 79 text
No content
Slide 80
Slide 80 text
struct SocialActivityRow: View {
let viewData: SocialActivityRowViewData
var body: some View {
HStack(spacing: .spacingS) {
Color.secondary
.overlay {
AsyncImage(url: viewData.profilePictureURL) { image in
image
.resizable()
.scaledToFill()
} placeholder: {
Color.gray
}
}
.frame(width: 48, height: 48)
.clipShape(Circle())
VStack(alignment: .leading) {
Text(viewData.message)
Text(viewData.time).foregroundStyle(.secondary)
}
.frame(maxWidth: .infinity, alignment: .leading)
Image(systemName: "hand.thumbsup")
.bold()
.font(.title2)
.foregroundStyle(.accent)
.padding(.spacingM)
Slide 81
Slide 81 text
No content
Slide 82
Slide 82 text
CustomAsyncImage
Slide 83
Slide 83 text
public enum ImageViewData: Equatable, Sendable {
case empty
case remote(url: URL)
case loading
case image(_ image: Image)
case error
}
Slide 84
Slide 84 text
private let allImageCases: [ImageViewData] = [
.loading,
.error,
.empty,
.image(Image(.bookCyclingInterval)),
.remote(from: URL(string: "https://randomuser.me/api/portraits/women/44.jpg")),
]
#Preview(traits: .sizeThatFitsLayout, arguments: allImageCases) { imageViewData in
CustomAsyncImage(state: imageViewData) { image in
image
.resizable()
.scaledToFill()
}
.frame(width: 300, height: 300)
.padding()
}
Slide 85
Slide 85 text
struct SocialActivityRow: View {
let viewData: SocialActivityRowViewData
var body: some View {
HStack(spacing: .spacingS) {
Color.secondary
.overlay {
AsyncImage(url: viewData.profilePictureURL) { image in
image
.resizable()
.scaledToFill()
} placeholder: {
Color.gray
}
}
.frame(width: 48, height: 48)
.clipShape(Circle())
VStack(alignment: .leading) {
Text(viewData.message)
Text(viewData.time).foregroundStyle(.secondary)
}
.frame(maxWidth: .infinity, alignment: .leading)
Image(systemName: "hand.thumbsup")
.bold()
.font(.title2)
.foregroundStyle(.accent)
.padding(.spacingM)
Slide 86
Slide 86 text
struct SocialActivityRow: View {
let viewData: SocialActivityRowViewData
var body: some View {
HStack(spacing: .spacingS) {
Color.secondary
.overlay {
CustomAsyncImage(state: viewData.profilePicture) { image in
image
.resizable()
.scaledToFill()
} placeholder: {
Color.gray
}
}
.frame(width: 48, height: 48)
.clipShape(Circle())
VStack(alignment: .leading) {
Text(viewData.message)
Text(viewData.time).foregroundStyle(.secondary)
}
.frame(maxWidth: .infinity, alignment: .leading)
Image(systemName: "hand.thumbsup")
.bold()
.font(.title2)
.foregroundStyle(.accent)
.padding(.spacingM)
Slide 87
Slide 87 text
No content
Slide 88
Slide 88 text
Practical problems to solve
Setting up Xcode Cloud
Controlling time zones
Controlling image loading
fl
The " ashing" problem
Slide 89
Slide 89 text
No content
Slide 90
Slide 90 text
No content
Slide 91
Slide 91 text
No content
Slide 92
Slide 92 text
struct SocialActivityRow: View {
let viewData: SocialActivityRowViewData
var body: some View {
HStack(spacing: .spacingS) {
AsyncImage(url: viewData.profilePictureURL) { image in
image
.resizable()
.scaledToFill()
.frame(width: 48, height: 48)
.clipShape(Circle())
} placeholder: {
Color.gray
}
// ...
}
}
}
Slide 93
Slide 93 text
@testable import NordicGym
import Testing
import SwiftUI
import SnapshotTesting
@MainActor @Suite struct `Social Row Tests` {
@Test(arguments: SnapshotVariant.defaultVariants(checkAccessibility: true))
func `social row in different configurations`(variant: SnapshotVariant) async throws {
let view = VStack {
row(.previewValue(profilePicture: .loading, isLiked: true))
row(.previewValue(profilePicture: .image(Image(.homeErikPortrait)), isLiked: false))
row(.previewValue(profilePicture: .none, isLiked: false))
row(.previewValue(
message: """
**Diego Fernando Morales Castañeda Fernandez** \
did the toughest class known to mankind
"""
))
}
.padding()
expectSnapshot(of: view, on: variant)
}
private func row(_ viewData: SocialActivityRowViewData) -> some View {
SocialActivityRow(viewData: viewData)
}
}
Slide 94
Slide 94 text
No content
Slide 95
Slide 95 text
view = f(state+)
Slide 96
Slide 96 text
Making UI Testable Better apps for people
No need to test all combinations Find the variants that cover the most
ground
No need to use ViewData Find your own abstractions
Slide 97
Slide 97 text
Slide
s, Sam
every
p
l
thing e code a
f
can b rom this nd
e fou
t
a
nd in lk
Slide 98
Slide 98 text
No content
Slide 99
Slide 99 text
/// Basic snapshot variants to test a screen on.
///
/// by default it will do:
/// - iPhone Light
/// - iPhone Dark
/// - iPad Portrait Light
/// - iPad Landscape Dark
/// - iPhone Portrait Light Accessibility 3*
/// - iPad Portrait Dark Accessibility 3*
///
/// - Parameters:
///
- navigationTitle: (default `nil`) If included, the view will be wrapped in a NavigationStack
///
- checkAccessibility: (default `false`), adds a variant that checks dynamic type with an `.accessibility` size
/// - Returns: An array of snapshot variants to test with
static func defaultVariants(
navigationTitle: String? = nil,
checkAccessibility: Bool = false
) -> [SnapshotVariant]
Slide 100
Slide 100 text
No content
Slide 101
Slide 101 text
No content
Slide 102
Slide 102 text
No content
Slide 103
Slide 103 text
No content
Slide 104
Slide 104 text
No content
Slide 105
Slide 105 text
No content
Slide 106
Slide 106 text
Reference
Failure
Slide 107
Slide 107 text
No content
Slide 108
Slide 108 text
There is a diff image in here
Slide 109
Slide 109 text
Image with colors and levels manipulated
Slide 110
Slide 110 text
No content
Slide 111
Slide 111 text
No content
Slide 112
Slide 112 text
/// A snapshot strategy for comparing SwiftUI Views based on pixel equality.
///
/// - Parameters:
///
- drawHierarchyInKeyWindow: Utilize the simulator's key window in order to render
///
`UIAppearance` and `UIVisualEffect`s. This option requires a host application for your
///
tests and will _not_ work for framework test targets.
///
- precision: The percentage of pixels that must match.
///
- perceptualPrecision: The percentage a pixel must match the source pixel to be considered a
///
match. 98-99% mimics
///
[the precision](http://zschuessler.github.io/DeltaE/learn/#toc-defining-delta-e) of the
///
human eye.
///
- layout: A view layout override.
///
- traits: A trait collection override.
public static func image(
drawHierarchyInKeyWindow: Bool = false,
precision: Float = 1,
perceptualPrecision: Float = 1,
layout: SwiftUISnapshotLayout = .sizeThatFits,
traits: UITraitCollection = .init()
)