aRustyDev SwiftUI Testing
Purpose
Testing strategies for SwiftUI applications including unit tests, UI tests, and preview-based testing.
XCTest Unit Testing
Testing ViewModels
import XCTest
@testable import MyApp
final class ItemViewModelTests: XCTestCase {
var sut: ItemViewModel!
var mockRepository: MockItemRepository!
override func setUp() {
super.setUp()
mockRepository = MockItemRepository()
sut = ItemViewModel(repository: mockRepository)
}
override func tearDown() {
sut = nil
mockRepository = nil
super.tearDown()
}
func test_loadItems_success_populatesItems() async {
// Given
let expectedItems = [Item(id: "1", name: "Test")]
mockRepository.items = expectedItems
// When
await sut.loadItems()
// Then
XCTAssertEqual(sut.items, expectedItems)
XCTAssertFalse(sut.isLoading)
XCTAssertNil(sut.errorMessage)
}
func test_loadItems_failure_setsError() async {
// Given
mockRepository.shouldFail = true
// When
await sut.loadItems()
// Then
XCTAssertTrue(sut.items.isEmpty)
XCTAssertNotNil(sut.errorMessage)
}
}
Testing @Observable Classes
import XCTest
@testable import MyApp
final class ShoppingCartTests: XCTestCase {
func test_addProduct_increasesQuantity() {
// Given
let cart = ShoppingCart()
let product = Product(id: "1", name: "Widget", price: 9.99)
// When
cart.add(product)
cart.add(product)
// Then
XCTAssertEqual(cart.items.count, 1)
XCTAssertEqual(cart.items.first?.quantity, 2)
}
func test_total_calculatesCorrectly() {
// Given
let cart = ShoppingCart()
cart.items = [
CartItem(productId: "1", price: 10.00, quantity: 2),
CartItem(productId: "2", price: 5.00, quantity: 1)
]
// Then
XCTAssertEqual(cart.total, 25.00)
}
}
Testing Async Code
func test_fetchData_withCancellation() async {
// Given
let viewModel = DataViewModel()
let task = Task {
await viewModel.fetchData()
}
// When
task.cancel()
await task.value
// Then
XCTAssertTrue(Task.isCancelled)
}
func test_fetchData_withTimeout() async throws {
// Given
let viewModel = SlowViewModel()
// When/Then - should complete within 5 seconds
try await withTimeout(seconds: 5) {
await viewModel.fetchData()
}
}
// Helper
func withTimeout<T>(seconds: Double, operation: @escaping () async throws -> T) async throws -> T {
try await withThrowingTaskGroup(of: T.self) { group in
group.addTask {
try await operation()
}
group.addTask {
try await Task.sleep(for: .seconds(seconds))
throw TimeoutError()
}
let result = try await group.next()!
group.cancelAll()
return result
}
}
XCUITest UI Testing
Basic UI Test Structure
import XCTest
final class ItemListUITests: XCTestCase {
var app: XCUIApplication!
override func setUp() {
super.setUp()
continueAfterFailure = false
app = XCUIApplication()
app.launchArguments = ["--uitesting"]
app.launch()
}
func test_addItem_appearsInList() {
// Given
let addButton = app.buttons["addItemButton"]
let nameField = app.textFields["itemNameField"]
let saveButton = app.buttons["saveButton"]
// When
addButton.tap()
nameField.tap()
nameField.typeText("New Item")
saveButton.tap()
// Then
let newItem = app.staticTexts["New Item"]
XCTAssertTrue(newItem.waitForExistence(timeout: 2))
}
}
Page Object Pattern
// Page object for Item List screen
struct ItemListPage {
let app: XCUIApplication
var addButton: XCUIElement {
app.buttons["addItemButton"]
}
var itemList: XCUIElement {
app.collectionViews["itemList"]
}
func item(named name: String) -> XCUIElement {
app.staticTexts[name]
}
func tapAdd() -> AddItemPage {
addButton.tap()
return AddItemPage(app: app)
}
func waitForItems() {
_ = itemList.waitForExistence(timeout: 5)
}
}
// Page object for Add Item screen
struct AddItemPage {
let app: XCUIApplication
var nameField: XCUIElement {
app.textFields["itemNameField"]
}
var saveButton: XCUIElement {
app.buttons["saveButton"]
}
func enterName(_ name: String) -> Self {
nameField.tap()
nameField.typeText(name)
return self
}
func save() -> ItemListPage {
saveButton.tap()
return ItemListPage(app: app)
}
}
// Usage in test
func test_addItem_pageObject() {
let listPage = ItemListPage(app: app)
listPage.waitForItems()
let result = listPage
.tapAdd()
.enterName("New Item")
.save()
XCTAssertTrue(result.item(named: "New Item").exists)
}
Accessibility Identifiers
// In SwiftUI View
struct ItemRow: View {
let item: Item
var body: some View {
HStack {
Text(item.name)
Spacer()
Button("Delete") {
// delete action
}
.accessibilityIdentifier("deleteButton-\(item.id)")
}
.accessibilityIdentifier("itemRow-\(item.id)")
}
}
// In UI Test
func test_deleteItem() {
let deleteButton = app.buttons["deleteButton-item123"]
deleteButton.tap()
let itemRow = app.otherElements["itemRow-item123"]
XCTAssertFalse(itemRow.exists)
}
ViewInspector Testing
import XCTest
import ViewInspector
@testable import MyApp
extension ItemRow: Inspectable {}
final class ItemRowTests: XCTestCase {
func test_displaysItemName() throws {
// Given
let item = Item(id: "1", name: "Test Item")
let view = ItemRow(item: item)
// When
let text = try view.inspect().find(text: "Test Item")
// Then
XCTAssertNotNil(text)
}
func test_deleteButton_callsOnDelete() throws {
// Given
var deleteCalled = false
let item = Item(id: "1", name: "Test")
let view = ItemRow(item: item, onDelete: { deleteCalled = true })
// When
try view.inspect().find(button: "Delete").tap()
// Then
XCTAssertTrue(deleteCalled)
}
}
Snapshot Testing
import XCTest
import SnapshotTesting
@testable import MyApp
final class ItemRowSnapshotTests: XCTestCase {
func test_itemRow_lightMode() {
let view = ItemRow(item: .preview)
.frame(width: 300)
.environment(\.colorScheme, .light)
assertSnapshot(of: view, as: .image)
}
func test_itemRow_darkMode() {
let view = ItemRow(item: .preview)
.frame(width: 300)
.environment(\.colorScheme, .dark)
assertSnapshot(of: view, as: .image)
}
func test_itemRow_dynamicType() {
for category in [ContentSizeCategory.extraSmall, .large, .accessibilityExtraExtraLarge] {
let view = ItemRow(item: .preview)
.frame(width: 300)
.environment(\.sizeCategory, category)
assertSnapshot(of: view, as: .image, named: "\(category)")
}
}
}
Preview-Based Testing
// Sample data for previews
extension Item {
static var preview: Item {
Item(id: "preview", name: "Preview Item", description: "A sample item")
}
static var previews: [Item] {
[
Item(id: "1", name: "First Item"),
Item(id: "2", name: "Second Item"),
Item(id: "3", name: "Third Item with a very long name that might wrap")
]
}
}
// Comprehensive preview
#Preview("Item Row - Standard") {
ItemRow(item: .preview)
}
#Preview("Item Row - Long Name") {
ItemRow(item: Item(id: "1", name: "This is a very long item name"))
}
#Preview("Item Row - Dark Mode") {
ItemRow(item: .preview)
.preferredColorScheme(.dark)
}
#Preview("Item List - Multiple") {
List(Item.previews) { item in
ItemRow(item: item)
}
}
Test Organization
Tests/
├── UnitTests/
│ ├── ViewModels/
│ │ └── ItemViewModelTests.swift
│ ├── Models/
│ │ └── ItemTests.swift
│ └── Services/
│ └── ItemRepositoryTests.swift
├── UITests/
│ ├── Pages/
│ │ ├── ItemListPage.swift
│ │ └── AddItemPage.swift
│ └── Flows/
│ └── ItemManagementTests.swift
└── SnapshotTests/
└── ItemRowSnapshotTests.swift
Best Practices
- Test ViewModels, not Views - Business logic testing
- Use dependency injection - Enable mocking
- Use accessibility identifiers - Stable UI test selectors
- Page object pattern - Maintainable UI tests
- Snapshot for visual regression - Catch unintended changes
Related Skills
- xctest-patterns: Advanced XCTest patterns
- swiftui-architecture: Testable architecture