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Zhongwei Li
540
skills/expertise/iphone-apps/references/testing.md
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540
skills/expertise/iphone-apps/references/testing.md
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# Testing
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Unit tests, UI tests, snapshot tests, and testing patterns for iOS apps.
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## Swift Testing (Xcode 16+)
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### Basic Tests
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```swift
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import Testing
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@testable import MyApp
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@Suite("Item Tests")
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struct ItemTests {
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@Test("Create item with name")
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func createItem() {
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let item = Item(name: "Test")
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#expect(item.name == "Test")
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#expect(item.isCompleted == false)
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}
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@Test("Toggle completion")
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func toggleCompletion() {
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var item = Item(name: "Test")
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item.isCompleted = true
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#expect(item.isCompleted == true)
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}
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}
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```
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### Async Tests
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```swift
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@Test("Fetch items from network")
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func fetchItems() async throws {
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let service = MockNetworkService()
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service.mockResult = [Item(name: "Test")]
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let viewModel = ItemListViewModel(networkService: service)
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await viewModel.load()
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#expect(viewModel.items.count == 1)
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#expect(viewModel.items[0].name == "Test")
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}
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@Test("Handle network error")
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func handleNetworkError() async {
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let service = MockNetworkService()
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service.mockError = NetworkError.noConnection
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let viewModel = ItemListViewModel(networkService: service)
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await viewModel.load()
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#expect(viewModel.items.isEmpty)
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#expect(viewModel.error != nil)
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}
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```
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### Parameterized Tests
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```swift
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@Test("Validate email", arguments: [
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("test@example.com", true),
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("invalid", false),
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("@example.com", false),
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("test@", false)
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])
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func validateEmail(email: String, expected: Bool) {
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let isValid = EmailValidator.isValid(email)
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#expect(isValid == expected)
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}
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```
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### Test Lifecycle
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```swift
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@Suite("Database Tests")
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struct DatabaseTests {
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let database: TestDatabase
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init() async throws {
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database = try await TestDatabase.create()
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}
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@Test func insertItem() async throws {
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try await database.insert(Item(name: "Test"))
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let items = try await database.fetchAll()
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#expect(items.count == 1)
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}
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}
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```
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## XCTest (Traditional)
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### Basic XCTest
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```swift
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import XCTest
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@testable import MyApp
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class ItemTests: XCTestCase {
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var sut: Item!
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override func setUp() {
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super.setUp()
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sut = Item(name: "Test")
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}
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override func tearDown() {
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sut = nil
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super.tearDown()
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}
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func testCreateItem() {
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XCTAssertEqual(sut.name, "Test")
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XCTAssertFalse(sut.isCompleted)
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}
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func testToggleCompletion() {
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sut.isCompleted = true
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XCTAssertTrue(sut.isCompleted)
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}
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}
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```
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### Async XCTest
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```swift
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func testFetchItems() async throws {
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let service = MockNetworkService()
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service.mockResult = [Item(name: "Test")]
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let viewModel = ItemListViewModel(networkService: service)
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await viewModel.load()
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XCTAssertEqual(viewModel.items.count, 1)
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}
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```
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## Mocking
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### Protocol-Based Mocks
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```swift
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// Protocol
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protocol NetworkServiceProtocol {
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func fetch<T: Decodable>(_ endpoint: Endpoint) async throws -> T
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}
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// Mock
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class MockNetworkService: NetworkServiceProtocol {
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var mockResult: Any?
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var mockError: Error?
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var fetchCallCount = 0
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func fetch<T: Decodable>(_ endpoint: Endpoint) async throws -> T {
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fetchCallCount += 1
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if let error = mockError {
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throw error
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}
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guard let result = mockResult as? T else {
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fatalError("Mock result type mismatch")
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}
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return result
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}
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}
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```
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### Testing with Mocks
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```swift
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@Test func loadItemsCallsNetwork() async {
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let mock = MockNetworkService()
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mock.mockResult = [Item]()
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let viewModel = ItemListViewModel(networkService: mock)
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await viewModel.load()
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#expect(mock.fetchCallCount == 1)
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}
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```
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## Testing SwiftUI Views
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### View Tests with ViewInspector
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```swift
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import ViewInspector
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@testable import MyApp
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@Test func itemRowDisplaysName() throws {
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let item = Item(name: "Test Item")
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let view = ItemRow(item: item)
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let text = try view.inspect().hStack().text(0).string()
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#expect(text == "Test Item")
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}
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```
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### Testing View Models
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```swift
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@Test func viewModelUpdatesOnSelection() async {
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let viewModel = ItemListViewModel()
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viewModel.items = [Item(name: "A"), Item(name: "B")]
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viewModel.select(viewModel.items[0])
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#expect(viewModel.selectedItem?.name == "A")
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}
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```
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## UI Testing
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### Basic UI Test
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```swift
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import XCTest
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class MyAppUITests: XCTestCase {
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let app = XCUIApplication()
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override func setUpWithError() throws {
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continueAfterFailure = false
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app.launchArguments = ["--uitesting"]
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app.launch()
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}
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func testAddItem() {
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// Tap add button
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app.buttons["Add"].tap()
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// Enter name
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let textField = app.textFields["Item name"]
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textField.tap()
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textField.typeText("New Item")
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// Save
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app.buttons["Save"].tap()
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// Verify
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XCTAssertTrue(app.staticTexts["New Item"].exists)
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}
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func testSwipeToDelete() {
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// Assume item exists
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let cell = app.cells["Item Row"].firstMatch
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// Swipe and delete
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cell.swipeLeft()
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app.buttons["Delete"].tap()
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// Verify
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XCTAssertFalse(cell.exists)
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}
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}
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```
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### Accessibility Identifiers
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```swift
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struct ItemRow: View {
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let item: Item
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var body: some View {
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HStack {
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Text(item.name)
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}
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.accessibilityIdentifier("Item Row")
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}
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}
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struct NewItemView: View {
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@State private var name = ""
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var body: some View {
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TextField("Item name", text: $name)
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.accessibilityIdentifier("Item name")
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}
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}
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```
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### Launch Arguments for Testing
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```swift
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@main
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struct MyApp: App {
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var body: some Scene {
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WindowGroup {
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ContentView()
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.onAppear {
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if CommandLine.arguments.contains("--uitesting") {
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// Use mock data
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// Skip onboarding
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// Clear state
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}
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}
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}
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}
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}
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```
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## Snapshot Testing
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Using swift-snapshot-testing:
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```swift
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import SnapshotTesting
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import XCTest
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@testable import MyApp
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class SnapshotTests: XCTestCase {
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func testItemRow() {
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let item = Item(name: "Test", subtitle: "Subtitle")
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let view = ItemRow(item: item)
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.frame(width: 375)
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assertSnapshot(of: view, as: .image)
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}
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func testItemRowDarkMode() {
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let item = Item(name: "Test", subtitle: "Subtitle")
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let view = ItemRow(item: item)
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.frame(width: 375)
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.preferredColorScheme(.dark)
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assertSnapshot(of: view, as: .image, named: "dark")
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}
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func testItemRowLargeText() {
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let item = Item(name: "Test", subtitle: "Subtitle")
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let view = ItemRow(item: item)
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.frame(width: 375)
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.environment(\.sizeCategory, .accessibilityExtraLarge)
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assertSnapshot(of: view, as: .image, named: "large-text")
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}
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}
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```
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## Testing SwiftData
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```swift
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@Suite("SwiftData Tests")
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struct SwiftDataTests {
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@Test func insertAndFetch() async throws {
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// In-memory container for testing
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let config = ModelConfiguration(isStoredInMemoryOnly: true)
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let container = try ModelContainer(for: Item.self, configurations: config)
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let context = container.mainContext
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// Insert
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let item = Item(name: "Test")
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context.insert(item)
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try context.save()
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// Fetch
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let descriptor = FetchDescriptor<Item>()
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let items = try context.fetch(descriptor)
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#expect(items.count == 1)
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#expect(items[0].name == "Test")
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}
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}
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```
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## Testing Network Calls
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### Using URLProtocol
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```swift
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class MockURLProtocol: URLProtocol {
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static var requestHandler: ((URLRequest) throws -> (HTTPURLResponse, Data))?
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override class func canInit(with request: URLRequest) -> Bool {
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return true
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}
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override class func canonicalRequest(for request: URLRequest) -> URLRequest {
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return request
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}
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override func startLoading() {
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guard let handler = MockURLProtocol.requestHandler else {
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fatalError("Handler not set")
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}
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do {
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let (response, data) = try handler(request)
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client?.urlProtocol(self, didReceive: response, cacheStoragePolicy: .notAllowed)
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client?.urlProtocol(self, didLoad: data)
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client?.urlProtocolDidFinishLoading(self)
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} catch {
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client?.urlProtocol(self, didFailWithError: error)
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}
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}
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override func stopLoading() {}
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}
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@Test func fetchItemsReturnsData() async throws {
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// Configure mock
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let config = URLSessionConfiguration.ephemeral
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config.protocolClasses = [MockURLProtocol.self]
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let session = URLSession(configuration: config)
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let mockItems = [Item(name: "Test")]
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let mockData = try JSONEncoder().encode(mockItems)
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MockURLProtocol.requestHandler = { request in
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let response = HTTPURLResponse(
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url: request.url!,
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statusCode: 200,
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httpVersion: nil,
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headerFields: nil
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)!
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return (response, mockData)
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}
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// Test
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let service = NetworkService(session: session)
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let items: [Item] = try await service.fetch(.items)
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#expect(items.count == 1)
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}
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```
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## Test Helpers
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### Factory Methods
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```swift
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extension Item {
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static func sample(
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name: String = "Sample",
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isCompleted: Bool = false,
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priority: Int = 0
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) -> Item {
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Item(name: name, isCompleted: isCompleted, priority: priority)
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}
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static var samples: [Item] {
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[
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.sample(name: "First"),
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.sample(name: "Second", isCompleted: true),
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.sample(name: "Third", priority: 5)
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]
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}
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}
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```
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### Async Test Utilities
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```swift
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func waitForCondition(
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timeout: TimeInterval = 1.0,
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condition: @escaping () -> Bool
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) async throws {
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let start = Date()
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while !condition() {
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if Date().timeIntervalSince(start) > timeout {
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throw TestError.timeout
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}
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try await Task.sleep(nanoseconds: 10_000_000) // 10ms
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}
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}
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enum TestError: Error {
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case timeout
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}
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```
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## Running Tests from CLI
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```bash
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# Run all tests
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xcodebuild test \
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-project MyApp.xcodeproj \
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-scheme MyApp \
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-destination 'platform=iOS Simulator,name=iPhone 16'
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# Run specific test
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xcodebuild test \
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-project MyApp.xcodeproj \
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-scheme MyApp \
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-destination 'platform=iOS Simulator,name=iPhone 16' \
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-only-testing:MyAppTests/ItemTests
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# With code coverage
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xcodebuild test \
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-project MyApp.xcodeproj \
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-scheme MyApp \
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-destination 'platform=iOS Simulator,name=iPhone 16' \
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-enableCodeCoverage YES \
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-resultBundlePath TestResults.xcresult
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```
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## Best Practices
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### Test Naming
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```swift
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// Describe what is being tested and expected outcome
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@Test func itemListViewModel_load_setsItemsFromNetwork()
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@Test func purchaseService_purchaseProduct_updatesEntitlements()
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```
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### Arrange-Act-Assert
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```swift
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@Test func toggleCompletion() {
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// Arrange
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var item = Item(name: "Test")
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// Act
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item.isCompleted.toggle()
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// Assert
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#expect(item.isCompleted == true)
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}
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```
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### One Assertion Per Test
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Focus each test on a single behavior:
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```swift
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// Good
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@Test func loadSetsItems() async { ... }
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@Test func loadSetsLoadingFalse() async { ... }
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@Test func loadClearsError() async { ... }
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// Avoid
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@Test func loadWorks() async {
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// Too many assertions
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}
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```
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Reference in New Issue
Block a user