Skill: Project Structure

Guide for project organization and directory structure.

When to use this skill

• Create a new feature module
• Organize files correctly
• Understand the codebase layout
• Add extensions to existing types

Project Overview

{AppName}/
├── App/
│   ├── Sources/
│   │   ├── {AppName}App.swift        # Minimal entry point (imports AppKit)
│   │   └── Resources/
│   │       └── Assets.xcassets/
│   └── Tests/
│       └── UI/                       # UI tests only
├── AppKit/                           # Testable app code (SPM local package)
│   ├── Package.swift
│   ├── Sources/
│   │   ├── AppContainer.swift        # Composition Root (centralized DI)
│   │   ├── Data/
│   │   │   └── AppEnvironment+API.swift
│   │   └── Presentation/
│   │       ├── Navigation/
│   │       │   └── AppNavigationRedirect.swift
│   │       └── Views/
│   │           └── RootContainerView.swift
│   └── Tests/
│       ├── Unit/                     # Unit tests
│       ├── Snapshots/                # Snapshot tests
│       └── Shared/                   # Shared resources
├── Features/                         # Each feature is an SPM local package
│   ├── {Feature}/
│   │   ├── Package.swift
│   │   └── ...
│   └── Home/
│       ├── Package.swift
│       └── ...
├── Libraries/                        # Each library is an SPM local package
│   ├── Core/
│   │   ├── Package.swift
│   │   └── ...
│   ├── Networking/
│   ├── DesignSystem/
│   └── SnapshotTestKit/
├── Shared/
│   └── Resources/
│       ├── Package.swift
│       └── ...
├── Derived/                          # Generated by Tuist (gitignored)
│   └── InfoPlists/
├── Tuist/
│   ├── ProjectDescriptionHelpers/
│   └── Package.swift               # External SPM dependencies + target settings
├── Project.swift                    # Root project (app + UI tests + module packages)
├── Workspace.swift                  # Workspace configuration (code coverage)
├── {AppName}.xctestplan            # Test plan aggregating all module test targets (SPM strategy only)
├── Tuist.swift
└── CLAUDE.md

Key Architecture:

• App: Minimal entry point that imports ChallengeAppKit
• AppKit: Framework containing testable app code (AppContainer, RootContainerView, AppNavigationRedirect). Tests run without TEST_HOST.

Feature Naming

Feature directory names must not contain the word "Feature". Use simple, descriptive names:

// RIGHT
Features/User/
Features/Character/
Features/Home/

// WRONG
Features/UserFeature/
Features/CharacterFeature/

Feature Module Structure

Each feature module follows this internal structure:

FeatureName/
├── Package.swift                            # SPM local package definition
├── Sources/
│   ├── {Feature}Feature.swift              # Public entry point (navigation + deep links)
│   ├── {Feature}Container.swift            # Dependency composition (factories)
│   ├── Domain/
│   │   ├── Models/
│   │   │   └── {Name}.swift                # Domain models
│   │   ├── UseCases/
│   │   │   └── Get{Name}UseCase.swift      # Business logic
│   │   └── Repositories/
│   │       └── {Name}RepositoryContract.swift  # Repository contracts
│   ├── Data/
│   │   ├── DataSources/
│   │   │   ├── Remote/
│   │   │   │   ├── {Name}RemoteDataSourceContract.swift
│   │   │   │   └── {Name}RESTDataSource.swift
│   │   │   └── Local/
│   │   │       ├── {Name}LocalDataSourceContract.swift
│   │   │       └── {Name}MemoryDataSource.swift
│   │   ├── DTOs/
│   │   │   └── {Name}DTO.swift
│   │   ├── Mappers/
│   │   │   └── {Name}Mapper.swift
│   │   └── Repositories/
│   │       └── {Name}Repository.swift
│   └── Presentation/
│       ├── Navigation/                             # Feature-level navigation (inside Presentation)
│       │   ├── {Feature}IncomingNavigation.swift   # Navigation destinations
│       │   ├── {Feature}OutgoingNavigation.swift   # Cross-feature navigation (optional)
│       │   └── {Feature}DeepLinkHandler.swift      # Deep link handler
│       ├── {Name}List/
│       │   ├── Navigator/
│       │   │   ├── {Name}ListNavigatorContract.swift
│       │   │   └── {Name}ListNavigator.swift
│       │   ├── Tracker/
│       │   │   ├── {Name}ListTrackerContract.swift
│       │   │   ├── {Name}ListTracker.swift
│       │   │   └── {Name}ListEvent.swift
│       │   ├── Views/
│       │   │   └── {Name}ListView.swift
│       │   └── ViewModels/
│       │       ├── {Name}ListViewModel.swift
│       │       └── {Name}ListViewState.swift
│       └── {Name}Detail/
│           ├── Navigator/
│           │   ├── {Name}DetailNavigatorContract.swift
│           │   └── {Name}DetailNavigator.swift
│           ├── Tracker/
│           │   ├── {Name}DetailTrackerContract.swift
│           │   ├── {Name}DetailTracker.swift
│           │   └── {Name}DetailEvent.swift
│           ├── Views/
│           │   └── {Name}DetailView.swift
│           └── ViewModels/
│               ├── {Name}DetailViewModel.swift
│               └── {Name}DetailViewState.swift
├── Tests/
│   ├── Unit/                                # Unit tests (Swift Testing)
│   │   ├── Domain/
│   │   │   └── UseCases/
│   │   │       └── Get{Name}UseCaseTests.swift
│   │   ├── Data/
│   │   │   ├── Repositories/
│   │   │   │   └── {Name}RepositoryTests.swift
│   │   ├── Presentation/
│   │   │   ├── Navigation/
│   │   │   │   └── {Feature}DeepLinkHandlerTests.swift
│   │   │   └── {Name}List/
│   │   │       └── ViewModels/
│   │   │           └── {Name}ListViewModelTests.swift
│   │   └── Feature/
│   │       └── {Feature}FeatureTests.swift
│   ├── Snapshots/                           # Snapshot tests (ChallengeSnapshotTestKit)
│   │   └── Presentation/
│   │       └── {Name}List/
│   │           ├── {Name}ListViewSnapshotTests.swift
│   │           └── __Snapshots__/
│   └── Shared/                              # Shared resources
│       ├── Stubs/
│       │   └── {Name}+Stub.swift
│       ├── Mocks/
│       │   ├── Get{Name}UseCaseMock.swift
│       │   └── {Name}RepositoryMock.swift
│       ├── Fixtures/
│       │   └── {name}.json
│       ├── Extensions/
│       │   └── {Name}ViewState+Equatable.swift
│       └── Resources/
│           └── test-avatar.jpg
└── Mocks/                                   # Public mocks (if needed)
    └── {Name}RepositoryMock.swift

Presentation Layer Organization

The Presentation layer groups related Views and ViewModels by feature name:

Presentation/
├── CharacterDetail/            # Feature: Character detail screen
│   ├── Navigator/
│   │   ├── CharacterDetailNavigatorContract.swift
│   │   └── CharacterDetailNavigator.swift
│   ├── Tracker/
│   │   ├── CharacterDetailTrackerContract.swift
│   │   ├── CharacterDetailTracker.swift
│   │   └── CharacterDetailEvent.swift
│   ├── Views/
│   │   └── CharacterDetailView.swift
│   └── ViewModels/
│       ├── CharacterDetailViewModel.swift
│       └── CharacterDetailViewState.swift
├── CharacterList/              # Feature: Character list screen
│   ├── Navigator/
│   │   ├── CharacterListNavigatorContract.swift
│   │   └── CharacterListNavigator.swift
│   ├── Tracker/
│   │   ├── CharacterListTrackerContract.swift
│   │   ├── CharacterListTracker.swift
│   │   └── CharacterListEvent.swift
│   ├── Views/
│   │   └── CharacterListView.swift
│   └── ViewModels/
│       ├── CharacterListViewModel.swift
│       └── CharacterListViewState.swift
└── ...

Naming conventions:

• Folder name matches the feature (e.g., CharacterDetail)
• Navigator: {Feature}Navigator.swift and {Feature}NavigatorContract.swift
• Tracker: {Feature}Tracker.swift, {Feature}TrackerContract.swift, and {Feature}Event.swift
• View: {Feature}View.swift
• ViewModel: {Feature}ViewModel.swift
• ViewState: {Feature}ViewState.swift

Extensions

Extensions of external framework types (Foundation, UIKit, SwiftUI, etc.) must be placed in an Extensions/ folder.

Location

Sources/
├── Extensions/
│   ├── URL+QueryItems.swift
│   ├── Date+Formatting.swift
│   └── String+Validation.swift
└── ...

Tests/
├── Extensions/
│   ├── URLSession+Mock.swift
│   ├── HTTPURLResponse+Mock.swift
│   └── URLRequest+BodyData.swift
└── ...

Naming Convention

Pattern: TypeName+Purpose.swift

swift
1// URL+QueryItems.swift
2extension URL {
3    func appendingQueryItems(_ items: [URLQueryItem]) -> URL { ... }
4}
5
6// URLSession+Mock.swift (in Tests)
7extension URLSession {
8    static func mockSession() -> URLSession { ... }
9}
10
11// Date+Formatting.swift
12extension Date {
13    func formatted(style: DateFormatter.Style) -> String { ... }
14}

Tests Directory Structure

Tests/
├── Unit/                         # Unit tests (Swift Testing)
│   ├── Domain/
│   │   └── UseCases/
│   │       └── Get{Name}UseCaseTests.swift
│   ├── Data/
│   │   ├── Repositories/
│   │   │   └── {Name}RepositoryTests.swift
│   │   └── DataSources/
│   │       ├── Remote/
│   │       │   └── {Name}RemoteDataSourceTests.swift
│   │       └── Local/
│   │           └── {Name}MemoryDataSourceTests.swift
│   ├── Presentation/
│   │   └── {ScreenName}/
│   │       └── ViewModels/
│   │           └── {ScreenName}ViewModelTests.swift
│   └── Feature/
│       └── {Feature}FeatureTests.swift
├── Snapshots/                    # Snapshot tests (ChallengeSnapshotTestKit)
│   └── Presentation/
│       └── {ScreenName}/
│           ├── {ScreenName}ViewSnapshotTests.swift
│           └── __Snapshots__/
├── UI/                           # UI tests (XCTest, App only)
└── Shared/                       # Shared resources (used by Unit, Snapshots, and UI)
    ├── Stubs/                    # Domain model test data
    │   ├── Character+Stub.swift
    │   └── Location+Stub.swift
    ├── Mocks/                    # Internal test mocks
    │   ├── Get{Name}UseCaseMock.swift
    │   └── {Name}RepositoryMock.swift
    ├── Fixtures/                 # JSON fixtures for DTOs
    │   ├── character.json
    │   └── character_list.json
    ├── Extensions/               # Test helpers (Equatable, etc.)
    │   └── {Name}ViewState+Equatable.swift
    ├── Scenarios/                # Reusable SwiftMockServer configurations (UI tests)
    │   └── UITestCase+Scenarios.swift
    └── Resources/                # Test images
        └── test-avatar.jpg

Mocks Location

FeatureName/
├── Mocks/                    # Public mocks ({AppName}FeatureNameMocks framework)
│   └── {Name}RepositoryMock.swift
└── Tests/
    └── Shared/
        └── Mocks/            # Internal test-only mocks
            └── {Name}DataSourceMock.swift

Core Module

Libraries/Core/
├── Sources/
│   ├── AppEnvironment/
│   │   └── AppEnvironment.swift      # Base environment enum
│   ├── Feature/
│   │   └── FeatureContract.swift      # Feature protocol
│   ├── Navigation/
│   │   ├── NavigationCoordinator.swift   # @Observable path manager
│   │   ├── NavigatorContract.swift       # Navigation protocol
│   │   ├── NavigationRedirectContract.swift
│   │   ├── Navigation.swift              # Base navigation protocol
│   │   ├── AnyNavigation.swift           # Type-erased wrapper
│   │   └── DeepLinkHandler.swift
│   ├── ImageLoader/
│   │   ├── ImageLoaderContract.swift
│   │   ├── CachedImageLoader.swift
│   │   ├── ImageLoaderEnvironment.swift
│   │   ├── DiskCache/
│   │   │   ├── ImageDiskCacheContract.swift
│   │   │   ├── ImageDiskCache.swift
│   │   │   ├── DiskCacheConfiguration.swift
│   │   │   ├── FileSystemContract.swift
│   │   │   └── FileSystem.swift
│   │   └── MemoryCache/
│   │       ├── ImageMemoryCacheContract.swift
│   │       └── ImageMemoryCache.swift
│   ├── Tracking/
│   │   ├── TrackerContract.swift
│   │   ├── Tracker.swift
│   │   ├── TrackingEventContract.swift
│   │   └── Providers/
│   │       ├── TrackingProviderContract.swift
│   │       └── ConsoleTrackingProvider.swift
│   └── Extensions/
│       └── ...
├── Tests/
│   └── Unit/
│       ├── AppEnvironment/
│       │   └── AppEnvironmentTests.swift
│       ├── Navigation/
│       │   └── NavigationCoordinatorTests.swift
│       └── Tracking/
│           ├── TrackerTests.swift
│           └── ConsoleTrackingProviderTests.swift
└── Mocks/
    ├── NavigatorMock.swift
    ├── TrackerMock.swift
    ├── ImageLoaderMock.swift
    └── Bundle+JSON.swift

Networking Module

Libraries/Networking/
├── Sources/
│   ├── HTTP/
│   │   ├── HTTPClient.swift
│   │   ├── HTTPClientContract.swift
│   │   ├── Endpoint.swift
│   │   ├── HTTPMethod.swift
│   │   └── HTTPError.swift
├── Tests/
│   └── Unit/
└── Mocks/
    └── HTTPClientMock.swift

Shared Directory

The Shared/ directory contains app-specific modules (not reusable across apps).

Resources Module

Shared/Resources/
├── Package.swift
├── Sources/
│   ├── Extensions/
│   │   └── String+Localized.swift    # localized() extension
│   └── Resources/
│       └── Localizable.xcstrings
└── Tests/

The Resources module provides:

• Localization: Centralized Localizable.xcstrings and String.localized() extension
• Bundle.module: Auto-generated by SPM for targets with resources

Derived Directory

Tuist generates files in Derived/ (gitignored):

Derived/
└── InfoPlists/
    ├── {AppName}-Info.plist
    └── {AppName}UITests-Info.plist

Contents: Only Info.plist files for the app and UI tests targets. Module Info.plists are managed by SPM.

No generated Swift code: disableBundleAccessors and disableSynthesizedResourceAccessors are enabled in Project.swift.

App and AppKit Directories

The app code is split into two modules:

• App: Minimal entry point with UI tests only
• AppKit: Testable app code (unit and snapshot tests run here without TEST_HOST)

App/
├── Sources/
│   ├── {AppName}App.swift        # Minimal entry point (imports AppKit)
│   └── Resources/
│       └── Assets.xcassets/
│           ├── AppIcon.appiconset/        # Production icon
│           ├── AppIconDev.appiconset/     # Development icon
│           └── AppIconStaging.appiconset/ # Staging icon
└── Tests/
    ├── Shared/
    │   ├── Robots/               # Robot pattern for UI interactions
    │   ├── Scenarios/            # Reusable SwiftMockServer configurations
    │   ├── Stubs/                # Test data helpers
    │   ├── Fixtures/             # JSON fixtures
    │   └── Resources/            # Test images
    └── UI/                       # UI tests only (XCTest)

AppKit/
├── Sources/
│   ├── AppContainer.swift        # Composition Root (centralized DI)
│   ├── Data/
│   │   └── AppEnvironment+API.swift  # API configuration extension
│   └── Presentation/
│       ├── Navigation/
│       │   └── AppNavigationRedirect.swift
│       └── Views/
│           └── RootContainerView.swift    # Root view with navigation
└── Tests/
    ├── Unit/                     # Unit tests (Swift Testing)
    │   ├── Data/
    │   │   └── AppEnvironment+APITests.swift
    │   └── Presentation/
    │       └── Navigation/
    │           ├── AppContainerNavigationTests.swift
    │           └── AppNavigationRedirectTests.swift
    ├── Snapshots/                # Snapshot tests
    │   └── Presentation/
    └── Shared/                   # Shared resources
        └── Stubs/

Why AppKit? Unit and snapshot tests for app-level code can run without launching the app (no TEST_HOST required).

File Naming Summary

Checklist

• App contains only {AppName}App.swift and UI tests (with Robots, Scenarios, Stubs, Fixtures)
• AppKit contains testable code: AppContainer.swift, RootContainerView.swift, AppNavigationRedirect.swift
• Feature folder does not contain "Feature" suffix
• {Feature}Container.swift for dependency composition
• {Feature}Feature.swift as public entry point with makeMainView() and resolve()
• Sources organized by layer: Domain, Data, Presentation
• Navigation folder inside Presentation/Navigation/
• Presentation organized by screen: {ScreenName}/Navigator/, {ScreenName}/Tracker/, {ScreenName}/Views/, {ScreenName}/ViewModels/
• Unit tests in Tests/Unit/ mirroring Sources structure
• Snapshot tests in Tests/Snapshots/
• Feature tests in Tests/Unit/Feature/
• Extensions in dedicated Extensions/ folder
• Extension files named {Type}+{Purpose}.swift
• Public mocks in Mocks/, internal mocks in Tests/Shared/Mocks/
• Stubs in Tests/Shared/Stubs/
• JSON fixtures in Tests/Shared/Fixtures/
• Test resources in Tests/Shared/Resources/
• Module has its own Package.swift with source, mocks, and test targets
• Module's test target is included in the Dev scheme (Framework: via testableTargets, SPM: via Challenge.xctestplan)
• Module's target settings are configured in Tuist/Package.swift