/test-generator

name: test-generator
description: Generate test templates for unit tests, integration tests, and UI tests using Swift Testing and XCTest. Use when adding tests to iOS/macOS apps.
allowed-tools: [Read, Write, Edit, Glob, Grep, Bash, AskUserQuestion]
last_verified: 2026-07-16
review_by: 2027-06-22
os_version: iOS 27 / macOS 27

Test Generator

Generate test templates for unit tests, integration tests, and UI tests in iOS/macOS apps.

When This Skill Activates

Use this skill when the user:

• Asks to "add tests" or "write tests" for their app
• Asks about unit testing, UI testing, or XCTest
• Wants to test ViewModels, services, or repositories
• Mentions TDD or test-driven development
• Asks about Swift Testing framework (`@Test`, `#expect`, `@Suite`)
• Wants mock objects or test helpers
• Asks about snapshot testing or preview tests

Decision Tree

What tests do you need?
|
+-- Unit tests for business logic
|   +-- Swift Testing (@Test, #expect) -- recommended for iOS 16+
|   +-- XCTest -- for iOS 13-15 support or existing XCTest projects
|
+-- Integration tests (component interactions)
|   +-- Protocol-based mocks with dependency injection
|
+-- UI tests
|   +-- XCUITest with Screen Object pattern
|
+-- Snapshot/preview tests
    +-- PreviewSnapshots or swift-snapshot-testing

Pre-Generation Checks

1. Project Context Detection

• [ ] Identify existing test targets and test runner
• [ ] Detect testing framework already in use (Swift Testing vs XCTest)
• [ ] Verify deployment target (Swift Testing requires iOS 16+ / macOS 13+)
• [ ] Identify project architecture pattern (MVVM, TCA, Repository, etc.)
• [ ] Locate source file directories

2. Conflict Detection

Search for existing test infrastructure:

Glob: **/*Tests.swift, **/*Tests/**/*.swift, **/*Spec.swift
Grep: "import XCTest" or "import Testing" or "@Suite" or "@Test"
Grep: "MockItemRepository" or "protocol.*Repository" or "class Mock"

If existing tests are found:

• Ask user whether to follow the existing framework (XCTest vs Swift Testing) or migrate
• Check for existing mock objects to reuse or extend
• Identify existing test helpers and factories

If a test target already exists:

• Add new tests to the existing target -- do NOT create a new target
• Follow the existing directory structure and naming conventions

3. Architecture Detection

Grep: "ViewModel" or "Reducer" or "UseCase" or "Repository" or "Service"
Glob: **/*ViewModel.swift, **/*Reducer.swift, **/*Repository.swift

This determines which test templates to generate (ViewModel tests, Reducer tests, etc.).

Configuration Questions

1. Testing Framework

• **Swift Testing** (Recommended, iOS 16+) - Modern, expressive syntax
• **XCTest** - Traditional framework, all iOS versions
• **Both** - Mix of frameworks

2. Test Types to Generate

• **Unit Tests** - Test individual components in isolation
• **Integration Tests** - Test component interactions
• **UI Tests** - Test user interface and flows
• **All** - Complete test coverage

3. Architecture Pattern

• **MVVM** - ViewModel tests
• **TCA** - Reducer tests
• **Repository** - Data layer tests
• **Custom** - Based on project structure

Generated Files

Unit Tests

Tests/UnitTests/
├── ViewModelTests/
│   └── ItemViewModelTests.swift
├── ServiceTests/
│   └── APIClientTests.swift
└── RepositoryTests/
    └── ItemRepositoryTests.swift

UI Tests

Tests/UITests/
├── Screens/
│   └── HomeScreenTests.swift
├── Flows/
│   └── OnboardingFlowTests.swift
└── Helpers/
    └── TestHelpers.swift

Swift Testing (Modern)

Basic Test Structure

import Testing
@testable import YourApp

@Suite("Item ViewModel Tests")
struct ItemViewModelTests {

    @Test("loads items successfully")
    func loadsItems() async throws {
        let mockRepository = MockItemRepository()
        let viewModel = ItemViewModel(repository: mockRepository)

        await viewModel.loadItems()

        #expect(viewModel.items.count == 3)
        #expect(viewModel.isLoading == false)
    }

    @Test("handles empty state")
    func handlesEmptyState() async {
        let mockRepository = MockItemRepository(items: [])
        let viewModel = ItemViewModel(repository: mockRepository)

        await viewModel.loadItems()

        #expect(viewModel.items.isEmpty)
        #expect(viewModel.showEmptyState)
    }
}

Parameterized Tests

@Test("validates email format", arguments: [
    ("valid@email.com", true),
    ("invalid", false),
    ("no@tld", false),
    ("test@domain.co.uk", true)
])
func validatesEmail(email: String, isValid: Bool) {
    #expect(EmailValidator.isValid(email) == isValid)
}

XCTest (Traditional)

Basic Test Structure

import XCTest
@testable import YourApp

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 testLoadsItems() async throws {
        await sut.loadItems()

        XCTAssertEqual(sut.items.count, 3)
        XCTAssertFalse(sut.isLoading)
    }
}

Test Patterns

Testing ViewModels

@Suite("ViewModel Tests")
struct ViewModelTests {

    @Test("state transitions correctly")
    func stateTransitions() async {
        let vm = ItemViewModel(repository: MockItemRepository())

        #expect(vm.state == .idle)

        await vm.loadItems()

        #expect(vm.state == .loaded)
    }

    @Test("error handling")
    func errorHandling() async {
        let failingRepo = MockItemRepository(shouldFail: true)
        let vm = ItemViewModel(repository: failingRepo)

        await vm.loadItems()

        #expect(vm.state == .error)
        #expect(vm.erro