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322 lines
8.4 KiB
Markdown
322 lines
8.4 KiB
Markdown
---
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name: csharp-testing
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description: 使用 xUnit、FluentAssertions、模拟、集成测试和测试组织最佳实践的 C# 和 .NET 测试模式。
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origin: ECC
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---
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# C# 测试模式
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使用 xUnit、FluentAssertions 和现代测试实践为 .NET 应用程序提供的全面测试模式。
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## 何时使用
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* 为 C# 代码编写新测试
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* 审查测试质量和覆盖率
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* 为 .NET 项目搭建测试基础设施
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* 调试不稳定或缓慢的测试
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## 测试框架栈
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| 工具 | 用途 |
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|---|---|
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| **xUnit** | 测试框架（.NET 首选） |
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| **FluentAssertions** | 可读的断言语法 |
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| **NSubstitute** 或 **Moq** | 模拟依赖项 |
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| **Testcontainers** | 集成测试中的真实基础设施 |
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| **WebApplicationFactory** | ASP.NET Core 集成测试 |
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| **Bogus** | 生成逼真的测试数据 |
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## 单元测试结构
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### 安排-操作-断言
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```csharp
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public sealed class OrderServiceTests
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{
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private readonly IOrderRepository _repository = Substitute.For<IOrderRepository>();
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private readonly ILogger<OrderService> _logger = Substitute.For<ILogger<OrderService>>();
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private readonly OrderService _sut;
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public OrderServiceTests()
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{
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_sut = new OrderService(_repository, _logger);
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}
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[Fact]
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public async Task PlaceOrderAsync_ReturnsSuccess_WhenRequestIsValid()
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{
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// Arrange
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var request = new CreateOrderRequest
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{
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CustomerId = "cust-123",
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Items = [new OrderItem("SKU-001", 2, 29.99m)]
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};
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// Act
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var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
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// Assert
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result.IsSuccess.Should().BeTrue();
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result.Value.Should().NotBeNull();
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result.Value!.CustomerId.Should().Be("cust-123");
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}
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[Fact]
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public async Task PlaceOrderAsync_ReturnsFailure_WhenNoItems()
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{
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// Arrange
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var request = new CreateOrderRequest
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{
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CustomerId = "cust-123",
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Items = []
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};
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// Act
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var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
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// Assert
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result.IsSuccess.Should().BeFalse();
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result.Error.Should().Contain("at least one item");
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}
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}
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```
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### 使用 Theory 的参数化测试
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```csharp
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[Theory]
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[InlineData("", false)]
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[InlineData("a", false)]
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[InlineData("ab@c.d", false)]
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[InlineData("user@example.com", true)]
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[InlineData("user+tag@example.co.uk", true)]
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public void IsValidEmail_ReturnsExpected(string email, bool expected)
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{
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EmailValidator.IsValid(email).Should().Be(expected);
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}
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[Theory]
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[MemberData(nameof(InvalidOrderCases))]
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public async Task PlaceOrderAsync_RejectsInvalidOrders(CreateOrderRequest request, string expectedError)
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{
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var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
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result.IsSuccess.Should().BeFalse();
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result.Error.Should().Contain(expectedError);
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}
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public static TheoryData<CreateOrderRequest, string> InvalidOrderCases => new()
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{
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{ new() { CustomerId = "", Items = [ValidItem()] }, "CustomerId" },
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{ new() { CustomerId = "c1", Items = [] }, "at least one item" },
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{ new() { CustomerId = "c1", Items = [new("", 1, 10m)] }, "SKU" },
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};
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```
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## 使用 NSubstitute 进行模拟
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```csharp
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[Fact]
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public async Task GetOrderAsync_ReturnsNull_WhenNotFound()
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{
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// Arrange
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var orderId = Guid.NewGuid();
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_repository.FindByIdAsync(orderId, Arg.Any<CancellationToken>())
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.Returns((Order?)null);
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// Act
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var result = await _sut.GetOrderAsync(orderId, CancellationToken.None);
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// Assert
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result.Should().BeNull();
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}
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[Fact]
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public async Task PlaceOrderAsync_PersistsOrder()
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{
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// Arrange
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var request = ValidOrderRequest();
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// Act
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await _sut.PlaceOrderAsync(request, CancellationToken.None);
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// Assert — verify the repository was called
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await _repository.Received(1).AddAsync(
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Arg.Is<Order>(o => o.CustomerId == request.CustomerId),
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Arg.Any<CancellationToken>());
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}
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```
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## ASP.NET Core 集成测试
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### WebApplicationFactory 设置
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```csharp
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public sealed class OrderApiTests : IClassFixture<WebApplicationFactory<Program>>
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{
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private readonly HttpClient _client;
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public OrderApiTests(WebApplicationFactory<Program> factory)
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{
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_client = factory.WithWebHostBuilder(builder =>
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{
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builder.ConfigureServices(services =>
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{
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// Replace real DB with in-memory for tests
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services.RemoveAll<DbContextOptions<AppDbContext>>();
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services.AddDbContext<AppDbContext>(options =>
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options.UseInMemoryDatabase("TestDb"));
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});
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}).CreateClient();
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}
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[Fact]
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public async Task GetOrder_Returns404_WhenNotFound()
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{
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var response = await _client.GetAsync($"/api/orders/{Guid.NewGuid()}");
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response.StatusCode.Should().Be(HttpStatusCode.NotFound);
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}
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[Fact]
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public async Task CreateOrder_Returns201_WithValidRequest()
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{
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var request = new CreateOrderRequest
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{
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CustomerId = "cust-1",
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Items = [new("SKU-001", 1, 19.99m)]
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};
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var response = await _client.PostAsJsonAsync("/api/orders", request);
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response.StatusCode.Should().Be(HttpStatusCode.Created);
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response.Headers.Location.Should().NotBeNull();
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}
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}
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```
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### 使用 Testcontainers 进行测试
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```csharp
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public sealed class PostgresOrderRepositoryTests : IAsyncLifetime
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{
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private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()
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.WithImage("postgres:16-alpine")
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.Build();
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private AppDbContext _db = null!;
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public async Task InitializeAsync()
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{
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await _postgres.StartAsync();
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var options = new DbContextOptionsBuilder<AppDbContext>()
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.UseNpgsql(_postgres.GetConnectionString())
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.Options;
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_db = new AppDbContext(options);
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await _db.Database.MigrateAsync();
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}
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public async Task DisposeAsync()
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{
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await _db.DisposeAsync();
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await _postgres.DisposeAsync();
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}
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[Fact]
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public async Task AddAsync_PersistsOrder()
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{
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var repo = new SqlOrderRepository(_db);
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var order = Order.Create("cust-1", [new OrderItem("SKU-001", 2, 10m)]);
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await repo.AddAsync(order, CancellationToken.None);
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var found = await repo.FindByIdAsync(order.Id, CancellationToken.None);
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found.Should().NotBeNull();
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found!.Items.Should().HaveCount(1);
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}
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}
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```
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## 测试组织
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```
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tests/
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MyApp.UnitTests/
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Services/
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OrderServiceTests.cs
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PaymentServiceTests.cs
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Validators/
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EmailValidatorTests.cs
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MyApp.IntegrationTests/
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Api/
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OrderApiTests.cs
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Repositories/
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OrderRepositoryTests.cs
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MyApp.TestHelpers/
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Builders/
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OrderBuilder.cs
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Fixtures/
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DatabaseFixture.cs
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```
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## 测试数据构建器
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```csharp
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public sealed class OrderBuilder
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{
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private string _customerId = "cust-default";
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private readonly List<OrderItem> _items = [new("SKU-001", 1, 10m)];
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public OrderBuilder WithCustomer(string customerId)
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{
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_customerId = customerId;
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return this;
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}
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public OrderBuilder WithItem(string sku, int quantity, decimal price)
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{
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_items.Add(new OrderItem(sku, quantity, price));
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return this;
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}
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public Order Build() => Order.Create(_customerId, _items);
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}
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// Usage in tests
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var order = new OrderBuilder()
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.WithCustomer("cust-vip")
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.WithItem("SKU-PREMIUM", 3, 99.99m)
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.Build();
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```
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## 常见反模式
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| 反模式 | 修复方法 |
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|---|---|
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| 测试实现细节 | 测试行为和结果 |
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| 共享的可变测试状态 | 每个测试使用新实例（xUnit 通过构造函数实现） |
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| 在异步测试中使用 `Thread.Sleep` | 使用带超时的 `Task.Delay` 或轮询辅助方法 |
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| 对 `ToString()` 输出进行断言 | 对类型化属性进行断言 |
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| 每个测试一个巨型断言 | 每个测试一个逻辑断言 |
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| 测试名称描述实现 | 按行为命名：`Method_ExpectedResult_WhenCondition` |
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| 忽略 `CancellationToken` | 始终传递并验证取消 |
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## 运行测试
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```bash
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# Run all tests
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dotnet test
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# Run with coverage
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dotnet test --collect:"XPlat Code Coverage"
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# Run specific project
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dotnet test tests/MyApp.UnitTests/
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# Filter by test name
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dotnet test --filter "FullyQualifiedName~OrderService"
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# Watch mode during development
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dotnet watch test --project tests/MyApp.UnitTests/
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```
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