SwiftUI Testing

Unit Testing ViewModels

@MainActor
final class ProfileViewModelTests: XCTestCase {
    var sut: ProfileViewModel!
    var mockRepository: MockUserRepository!

    override func setUp() {
        super.setUp()
        mockRepository = MockUserRepository()
        sut = ProfileViewModel(repository: mockRepository)
    }

    override func tearDown() {
        sut = nil
        mockRepository = nil
        super.tearDown()
    }

    func testLoadUser_Success() async {
        // Given
        let expectedUser = User(id: "1", name: "John")
        mockRepository.stubbedUser = expectedUser

        // When
        await sut.loadUser(id: "1")

        // Then
        XCTAssertEqual(sut.user, expectedUser)
        XCTAssertFalse(sut.isLoading)
        XCTAssertNil(sut.error)
    }

    func testLoadUser_Failure() async {
        // Given
        mockRepository.shouldFail = true

        // When
        await sut.loadUser(id: "1")

        // Then
        XCTAssertNil(sut.user)
        XCTAssertNotNil(sut.error)
    }
}

Mock Repository Pattern

final class MockUserRepository: UserRepositoryProtocol, @unchecked Sendable {
    var stubbedUser: User?
    var shouldFail = false
    var fetchCallCount = 0

    func fetch(id: String) async throws -> User {
        fetchCallCount += 1
        if shouldFail {
            throw NSError(domain: "Test", code: -1)
        }
        return stubbedUser ?? User(id: id, name: "Test")
    }
}

UI Testing with Accessibility

final class ProfileUITests: XCTestCase {
    var app: XCUIApplication!

    override func setUp() {
        continueAfterFailure = false
        app = XCUIApplication()
        app.launchArguments = ["UI_TESTING"]
        app.launch()
    }

    func testProfileFlow() {
        // Navigate to profile
        let profileTab = app.tabBars.buttons["Profile"]
        XCTAssertTrue(profileTab.waitForExistence(timeout: 5))
        profileTab.tap()

        // Verify content
        let nameLabel = app.staticTexts["profileNameLabel"]
        XCTAssertTrue(nameLabel.exists)

        // Edit action
        app.buttons["editButton"].tap()
        let textField = app.textFields["nameTextField"]
        textField.clearAndType("New Name")
        app.buttons["saveButton"].tap()

        // Verify update
        XCTAssertEqual(nameLabel.label, "New Name")
    }
}

extension XCUIElement {
    func clearAndType(_ text: String) {
        guard let value = self.value as? String else { return }
        tap()
        let deleteString = String(repeating: XCUIKeyboardKey.delete.rawValue,
                                  count: value.count)
        typeText(deleteString)
        typeText(text)
    }
}

Snapshot Testing

import XCTest
import SnapshotTesting

final class ComponentSnapshotTests: XCTestCase {
    func testProfileCard_Light() {
        let view = ProfileCard(user: .mock)
            .frame(width: 300)

        assertSnapshot(of: view, as: .image(traits: .init(userInterfaceStyle: .light)))
    }

    func testProfileCard_Dark() {
        let view = ProfileCard(user: .mock)
            .frame(width: 300)

        assertSnapshot(of: view, as: .image(traits: .init(userInterfaceStyle: .dark)))
    }

    func testProfileCard_DynamicType() {
        let view = ProfileCard(user: .mock)
            .frame(width: 300)
            .environment(\.sizeCategory, .accessibilityExtraLarge)

        assertSnapshot(of: view, as: .image)
    }
}

Testing Async Code

func testAsyncDataLoad() async throws {
    // No need for expectations with async/await
    let result = try await sut.fetchData()
    XCTAssertFalse(result.isEmpty)
}

func testTaskCancellation() async {
    let task = Task {
        try await sut.longRunningOperation()
    }

    task.cancel()

    do {
        _ = try await task.value
        XCTFail("Should throw cancellation error")
    } catch is CancellationError {
        // Expected
    }
}