通过xUnit等实现示例编写和审查C#与.NET测试，涵盖单元测试、API和数据库集成测试，并整理测试数据与项目目录，以验证行为和结果。
C# and .NET testing patterns with xUnit, FluentAssertions, mocking, integration tests, and test organization best practices. Use when writing or reviewing xUnit tests, mocks, or integration tests in a C# / .NET project.
提供编写和审查C#与.NET测试的实现示例及组织方法，涵盖使用xUnit编写单元测试、使用FluentAssertions验证结果，以及用模拟对象替代依赖项。示例按准备、执行、验证的顺序组织，也展示如何用多组输入验证同一操作。
适合检查服务的成功与失败情形、ASP.NET Core API响应，以及数据库保存结果。还可整理测试数据的构建方式、共用准备步骤，以及单元测试和集成测试的目录布局。检查不稳定或运行缓慢的测试时，也可将其作为参考。
面向C#与.NET。示例使用NSubstitute、WebApplicationFactory和Testcontainers等工具，其中Testcontainers会启动真实的PostgreSQL实例。运行测试和收集覆盖率使用dotnet test。
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Comprehensive testing patterns for .NET applications using xUnit, FluentAssertions, and modern testing practices.
| Tool | Purpose |
|---|---|
| xUnit | Test framework (preferred for .NET) |
| FluentAssertions | Readable assertion syntax |
| NSubstitute or Moq | Mocking dependencies |
| Testcontainers | Real infrastructure in integration tests |
| WebApplicationFactory | ASP.NET Core integration tests |
| Bogus | Realistic test data generation |
public sealed class OrderServiceTests
{
private readonly IOrderRepository _repository = Substitute.For<IOrderRepository>();
private readonly ILogger<OrderService> _logger = Substitute.For<ILogger<OrderService>>();
private readonly OrderService _sut;
public OrderServiceTests()
{
_sut = new OrderService(_repository, _logger);
}
[Fact]
public async Task PlaceOrderAsync_ReturnsSuccess_WhenRequestIsValid()
{
// Arrange
var request = new CreateOrderRequest
{
CustomerId = "cust-123",
Items = [new OrderItem("SKU-001", 2, 29.99m)]
};
// Act
var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
// Assert
result.IsSuccess.Should().BeTrue();
result.Value.Should().NotBeNull();
result.Value!.CustomerId.Should().Be("cust-123");
}
[Fact]
public async Task PlaceOrderAsync_ReturnsFailure_WhenNoItems()
{
// Arrange
var request = new CreateOrderRequest
{
CustomerId = "cust-123",
Items = []
};
// Act
var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
// Assert
result.IsSuccess.Should().BeFalse();
result.Error.Should().Contain("at least one item");
}
}
[Theory]
[InlineData("", false)]
[InlineData("a", false)]
[InlineData("ab@c.d", false)]
[InlineData("user@example.com", true)]
[InlineData("user+tag@example.co.uk", true)]
public void IsValidEmail_ReturnsExpected(string email, bool expected)
{
EmailValidator.IsValid(email).Should().Be(expected);
}
[Theory]
[MemberData(nameof(InvalidOrderCases))]
public async Task PlaceOrderAsync_RejectsInvalidOrders(CreateOrderRequest request, string expectedError)
{
var result = await _sut.PlaceOrderAsync(request, CancellationToken.None);
result.IsSuccess.Should().BeFalse();
result.Error.Should().Contain(expectedError);
}
public static TheoryData<CreateOrderRequest, string> InvalidOrderCases => new()
{
{ new() { CustomerId = "", Items = [ValidItem()] }, "CustomerId" },
{ new() { CustomerId = "c1", Items = [] }, "at least one item" },
{ new() { CustomerId = "c1", Items = [new("", 1, 10m)] }, "SKU" },
};
[Fact]
public async Task GetOrderAsync_ReturnsNull_WhenNotFound()
{
// Arrange
var orderId = Guid.NewGuid();
_repository.FindByIdAsync(orderId, Arg.Any<CancellationToken>())
.Returns((Order?)null);
// Act
var result = await _sut.GetOrderAsync(orderId, CancellationToken.None);
// Assert
result.Should().BeNull();
}
[Fact]
public async Task PlaceOrderAsync_PersistsOrder()
{
// Arrange
var request = ValidOrderRequest();
// Act
await _sut.PlaceOrderAsync(request, CancellationToken.None);
// Assert — verify the repository was called
await _repository.Received(1).AddAsync(
Arg.Is<Order>(o => o.CustomerId == request.CustomerId),
Arg.Any<CancellationToken>());
}
public sealed class OrderApiTests : IClassFixture<WebApplicationFactory<Program>>
{
private readonly HttpClient _client;
public OrderApiTests(WebApplicationFactory<Program> factory)
{
_client = factory.WithWebHostBuilder(builder =>
{
builder.ConfigureServices(services =>
{
// Replace real DB with in-memory for tests
services.RemoveAll<DbContextOptions<AppDbContext>>();
services.AddDbContext<AppDbContext>(options =>
options.UseInMemoryDatabase("TestDb"));
});
}).CreateClient();
}
[Fact]
public async Task GetOrder_Returns404_WhenNotFound()
{
var response = await _client.GetAsync($"/api/orders/{Guid.NewGuid()}");
response.StatusCode.Should().Be(HttpStatusCode.NotFound);
}
[Fact]
public async Task CreateOrder_Returns201_WithValidRequest()
{
var request = new CreateOrderRequest
{
CustomerId = "cust-1",
Items = [new("SKU-001", 1, 19.99m)]
};
var response = await _client.PostAsJsonAsync("/api/orders", request);
response.StatusCode.Should().Be(HttpStatusCode.Created);
response.Headers.Location.Should().NotBeNull();
}
}
public sealed class PostgresOrderRepositoryTests : IAsyncLifetime
{
private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()
.WithImage("postgres:16-alpine")
.Build();
private AppDbContext _db = null!;
public async Task InitializeAsync()
{
await _postgres.StartAsync();
var options = new DbContextOptionsBuilder<AppDbContext>()
.UseNpgsql(_postgres.GetConnectionString())
.Options;
_db = new AppDbContext(options);
await _db.Database.MigrateAsync();
}
public async Task DisposeAsync()
{
await _db.DisposeAsync();
await _postgres.DisposeAsync();
}
[Fact]
public async Task AddAsync_PersistsOrder()
{
var repo = new SqlOrderRepository(_db);
var order = Order.Create("cust-1", [new OrderItem("SKU-001", 2, 10m)]);
await repo.AddAsync(order, CancellationToken.None);
var found = await repo.FindByIdAsync(order.Id, CancellationToken.None);
found.Should().NotBeNull();
found!.Items.Should().HaveCount(1);
}
}
tests/
MyApp.UnitTests/
Services/
OrderServiceTests.cs
PaymentServiceTests.cs
Validators/
EmailValidatorTests.cs
MyApp.IntegrationTests/
Api/
OrderApiTests.cs
Repositories/
OrderRepositoryTests.cs
MyApp.TestHelpers/
Builders/
OrderBuilder.cs
Fixtures/
DatabaseFixture.cs
public sealed class OrderBuilder
{
private string _customerId = "cust-default";
private readonly List<OrderItem> _items = [new("SKU-001", 1, 10m)];
public OrderBuilder WithCustomer(string customerId)
{
_customerId = customerId;
return this;
}
public OrderBuilder WithItem(string sku, int quantity, decimal price)
{
_items.Add(new OrderItem(sku, quantity, price));
return this;
}
public Order Build() => Order.Create(_customerId, _items);
}
// Usage in tests
var order = new OrderBuilder()
.WithCustomer("cust-vip")
.WithItem("SKU-PREMIUM", 3, 99.99m)
.Build();
| Anti-Pattern | Fix |
|---|---|
| Testing implementation details | Test behavior and outcomes |
| Shared mutable test state | Fresh instance per test (xUnit does this via constructors) |
Thread.Sleep in async tests | Use Task.Delay with timeout, or polling helpers |
Asserting on ToString() output | Assert on typed properties |
| One giant assertion per test | One logical assertion per test |
| Test names describing implementation | Name by behavior: Method_ExpectedResult_WhenCondition |
Ignoring CancellationToken | Always pass and verify cancellation |
# Run all tests
dotnet test
# Run with coverage
dotnet test --collect:"XPlat Code Coverage"
# Run specific project
dotnet test tests/MyApp.UnitTests/
# Filter by test name
dotnet test --filter "FullyQualifiedName~OrderService"
# Watch mode during development
dotnet watch test --project tests/MyApp.UnitTests/
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Design and audit interfaces for Web, iOS, and Android using WCAG 2.2 accessibility guidance. Check screen-reader labels, keyboard navigation, contrast, and control sizes to identify barriers and guide implementation for people using assistive technology.
中文简介正在准备中。当前显示英语简介。
从指令、记忆、工具执行和界面显示等十二个层面排查人工智能代理故障，依据代码和日志梳理原因，按严重程度列出问题并提出修复方案。
用实际开发任务比较多个编程智能体，记录成功率、可获取的API费用、耗时和重复运行的稳定性，为工具选型及更新后的性能评估提供数据。
Design and refine an AI agent’s available actions, tool inputs, and result formats. Define recovery steps for errors, manage the information kept in context, and evaluate changes through completion rates, retries, and cost per successful task.
中文简介正在准备中。当前显示英语简介。
根据错误信息和执行环境，分析AI代理反复失败或重复操作的原因。通过小范围、可撤销的恢复操作检验假设，并将结果与依据整理成可供交接的报告。
在AI代理反复失败或重复操作时，记录错误与环境前提、排查原因，采取影响有限的恢复操作，并汇总结果和证据，为有依据的重试与交接提供支持。