第 10 章：测试 SwiftData 应用

// 定义数据操作协议
protocol DataManagerProtocol {
    func fetchItems(predicate: Predicate<Item>?) throws -> [Item]
    func saveItem(_ item: Item) throws
    func deleteItem(_ item: Item) throws
}

// 实现具体类型
class SwiftDataManager: DataManagerProtocol {
    private let context: ModelContext
    
    init(context: ModelContext) {
        self.context = context
    }
    
    func fetchItems(predicate: Predicate<Item>?) throws -> [Item] {
        let descriptor = FetchDescriptor<Item>(predicate: predicate)
        return try context.fetch(descriptor)
    }
    
    // ...其他方法实现
}

class DataManagerTests: XCTestCase {
    private var testContainer: ModelContainer!
    private var testContext: ModelContext!
    
    override func setUp() {
        let config = ModelConfiguration(isStoredInMemoryOnly: true)
        testContainer = try! ModelContainer(for: Item.self, configurations: config)
        testContext = testContainer.mainContext
    }
    
    func testFetchEmptyItems() throws {
        let manager = SwiftDataManager(context: testContext)
        let items = try manager.fetchItems(predicate: nil)
        XCTAssertTrue(items.isEmpty)
    }
}

class MockDataManager: DataManagerProtocol {
    var mockItems: [Item] = []
    var lastSavedItem: Item?
    
    func fetchItems(predicate: Predicate<Item>?) throws -> [Item] {
        return mockItems
    }
    
    func saveItem(_ item: Item) throws {
        lastSavedItem = item
    }
    
    // ...其他mock实现
}

class ViewModelTests: XCTestCase {
    func testViewModelLoadsItems() {
        let mockManager = MockDataManager()
        mockManager.mockItems = [Item(name: "Test")]
        
        let viewModel = MyViewModel(dataManager: mockManager)
        viewModel.loadItems()
        
        XCTAssertEqual(viewModel.items.count, 1)
    }
}

func testPredicateFiltering() throws {
    let manager = SwiftDataManager(context: testContext)
    
    // 添加测试数据
    let item1 = Item(name: "Important", isCompleted: false)
    let item2 = Item(name: "Trivial", isCompleted: true)
    try manager.saveItem(item1)
    try manager.saveItem(item2)
    
    // 测试谓词
    let predicate = #Predicate<Item> { $0.isCompleted == false }
    let results = try manager.fetchItems(predicate: predicate)
    
    XCTAssertEqual(results.count, 1)
    XCTAssertEqual(results.first?.name, "Important")
}

func testAsyncOperations() async throws {
    let manager = SwiftDataManager(context: testContext)
    let newItem = Item(name: "Async Test")
    
    // 在主线程外执行保存
    try await Task.detached {
        try manager.saveItem(newItem)
    }.value
    
    // 验证结果
    let items = try manager.fetchItems(predicate: nil)
    XCTAssertEqual(items.count, 1)
}

func testSaveErrorHandling() {
    let manager = SwiftDataManager(context: testContext)
    let invalidItem = Item(name: "") // 假设空名称无效
    
    XCTAssertThrowsError(try manager.saveItem(invalidItem)) { error in
        XCTAssertTrue(error is ValidationError)
    }
}