[TDD] Integrating AuthManager and SessionManager

Since we are following a dependency injection pattern, both AuthManager and SessionManager will depend on a storage solution for user data persistence (e.g., SessionStorage).

Refactored AuthManager

protocol AuthServiceProtocol {
    func signIn(completion: @escaping (User?) -> Void)
    func signOut()
}

class AuthManager {
  private let authService: AuthServiceProtocol
  private let sessionManager: SessionManager
  
  init(
    authService: AuthServiceProtocol,
    sessionManager: SessionManager
  ) {
    self.authService = authService
    self.sessionManager = sessionManager
  }
  
  func signIn(callback: @escaping (User?) -> Void) {
    authService.signIn { [weak self] user in
      if let user = user {
        self?.sessionManager.saveUser(user)
      }
      callback(user)
    }
  }
  
  func signOut() {
    authService.signOut()
  }
}

Now that AuthManager and SessionManager are integrated, you can write tests for this flow to make sure sign-in and sign-out behavior works as expected.

class AuthManagerTests: XCTestCase {
  var authManager: AuthManager!
  var mockAuthService: MockAuthService!
  var mockStorage: MockStorage!
  
  override func setUp() {
    super.setUp()
    mockStorage = MockStorage()
    let sessionManager = SessionManager(storage: mockStorage)
    mockAuthService = MockAuthService()
    authManager = AuthManager(
      authService: mockAuthService,
      sessionManager: sessionManager)
  }
  
  func testSignInSuccess() {
    mockAuthService.user = User(id: 123, name: "John Doe", email: "john@example.com")
    let expectation = self.expectation(description: "Sign in should succeed")
    
    authManager.signIn { user in
      XCTAssertNotNil(user, "User should be not nil")
      XCTAssertNotNil(self.mockStorage.storageUser, "User should be saved to session")
      expectation.fulfill()
    }
    
    wait(for: [expectation], timeout: 1.0)
  }
  
  func testSignInFailure() {
    mockAuthService.user = nil
    let expectation = self.expectation(description: "Sign in should fail")
    
    authManager.signIn { user in
      XCTAssertNil(user, "Expected sign-in to be fail")
      expectation.fulfill()
    }
    
    wait(for: [expectation], timeout: 1.0)
  }
  
  func testSignOut() {
    authManager.signOut()
    XCTAssert(true, "Sign-out function executed succesfully")
  }
}

• AuthManager handles authentication logic and relies on SessionManager to persist the user session.
• SessionManager abstracts the session persistence mechanism, allowing you to easily swap storage (e.g., UserDefaults, Keychain) later.
• Unit tests ensure correctness by mocking both authentication and session storage behavior, so no real API calls or storage operations are made during tests.