[TDD] AuthManager When Sign-in Service Is Not Decided

Instead of writing logic directly inside AuthManager, we abstract it using AuthServiceProtocol.

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

class AuthManager {
    private let authService: AuthServiceProtocol
    
    init(authService: AuthServiceProtocol) {
        self.authService = authService
    }

    func signIn(callback: @escaping (Bool) -> Void) {
        authService.signIn { success in
            callback(success)
        }
    }

    func signOut() {
        authService.signOut()
    }
}

• AuthManager now works independently of Google/Facebook.
• We can inject a mock service for testing.
• The real sign-in logic can be implemented later.

Since we don’t have Google/Facebook auth yet, we create a mock service that simulates login/logout behavior.

class MockAuthService: AuthServiceProtocol {
    var isSignInSuccessful = true

    func signIn(completion: @escaping (Bool) -> Void) {
        completion(isSignInSuccessful) // Simulates login result
    }

    func signOut() {
        print("User signed out")
    }
}

• We avoid calling real authentication APIs in tests.
• We can control the sign-in success/failure behavior.

Now, we can test AuthManager using XCTest.

import XCTest

class AuthManagerTests: XCTestCase {
    var authManager: AuthManager!
    var mockAuthService: MockAuthService!

    override func setUp() {
        super.setUp()
        mockAuthService = MockAuthService()
        authManager = AuthManager(authService: mockAuthService)
    }

    func testSignInSuccess() {
        mockAuthService.isSignInSuccessful = true
        let expectation = self.expectation(description: "Sign-in should succeed")

        authManager.signIn { success in
            XCTAssertTrue(success, "Expected sign-in to be successful")
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 1.0)
    }

    func testSignInFailure() {
        mockAuthService.isSignInSuccessful = false
        let expectation = self.expectation(description: "Sign-in should fail")

        authManager.signIn { success in
            XCTAssertFalse(success, "Expected sign-in to fail")
            expectation.fulfill()
        }

        wait(for: [expectation], timeout: 1.0)
    }

    func testSignOut() {
        // No need for an async expectation since signOut() is synchronous
        authManager.signOut()
        XCTAssert(true, "Sign-out function executed successfully")
    }
}

• testSignInSuccess → Simulates a successful login.
• testSignInFailure → Simulates a failed login.
• testSignOut → Ensures signOut() runs without errors.