Testing

codewithmukesh/dotnet-claude-kit/skills/testing

作者 codewithmukesh23300897f4d1无许可证754 个星标收录于 2026年10月8日更新于 2026年10月8日仓库2个月前更新

Testing strategy for .NET 10 applications. Covers xUnit v3, WebApplicationFactory for integration tests, Testcontainers for real database testing, Verify for snapshot testing, and the AAA pattern. Load this skill when writing tests, setting up test infrastructure, reviewing test coverage, or when the user mentions "test", "xUnit", "WebApplicationFactory", "Testcontainers", "integration test", "unit test", "bUnit", "snapshot test", "Verify", "test coverage", "AAA pattern", "WireMock", or "FakeTimeProvider".

仅含说明

Testing (.NET 10)

Core Principles

  1. Integration tests are the highest-value tests — A single WebApplicationFactory test covers routing, binding, validation, business logic, and persistence in one shot. Start here before writing unit tests.
  2. Real databases in tests — Use Testcontainers to spin up real PostgreSQL/SQL Server instances. In-memory providers hide real bugs (transactions, constraints, SQL generation).
  3. AAA pattern is mandatory — Every test has three clearly separated sections: Arrange, Act, Assert. No mixing.
  4. Test behavior, not implementation — Tests should survive refactoring. Test what the system does, not how it does it.

Patterns

xUnit v3 Basics

csharp
public class OrderServiceTests{    [Fact]    public async Task CreateOrder_WithValidItems_ReturnsSuccessResult()    {        // Arrange        var db = CreateInMemoryDb();        var clock = new FakeTimeProvider(new DateTimeOffset(2025, 1, 15, 0, 0, 0, TimeSpan.Zero));        var service = new OrderService(db, clock);        var request = new CreateOrderRequest("customer-1", [new("product-1", 2)]);
        // Act        var result = await service.CreateAsync(request);
        // Assert        Assert.True(result.IsSuccess);        Assert.NotEqual(Guid.Empty, result.Value.Id);        Assert.Equal(clock.GetUtcNow(), result.Value.CreatedAt);    }
    [Theory]    [InlineData("")]    [InlineData(null)]    public async Task CreateOrder_WithInvalidCustomerId_ReturnsFailure(string? customerId)    {        // Arrange        var service = CreateService();
        // Act        var result = await service.CreateAsync(new CreateOrderRequest(customerId!, []));
        // Assert        Assert.False(result.IsSuccess);    }}

Integration Tests with WebApplicationFactory

The highest-value test pattern. Tests the full HTTP pipeline.

csharp
// Fixtures/ApiFixture.cspublic class ApiFixture : WebApplicationFactory<Program>, IAsyncLifetime{    private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()        .WithImage("postgres:18")        .Build();
    protected override void ConfigureWebHost(IWebHostBuilder builder)    {        builder.ConfigureServices(services =>        {            // Replace the real DB with Testcontainers            services.RemoveAll<DbContextOptions<AppDbContext>>();            services.AddDbContext<AppDbContext>(options =>                options.UseNpgsql(_postgres.GetConnectionString()));        });    }
    // xUnit v3: IAsyncLifetime.InitializeAsync returns ValueTask (v2 used Task)    public async ValueTask InitializeAsync()    {        await _postgres.StartAsync();
        // Apply migrations        using var scope = Services.CreateScope();        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();        await db.Database.MigrateAsync();    }
    // xUnit v3: IAsyncLifetime inherits IAsyncDisposable — override the    // ValueTask DisposeAsync that WebApplicationFactory already provides    public override async ValueTask DisposeAsync()    {        await _postgres.DisposeAsync();        await base.DisposeAsync();    }}
csharp
// Tests/Orders/CreateOrderTests.cspublic class CreateOrderTests(ApiFixture fixture) : IClassFixture<ApiFixture>{    private readonly HttpClient _client = fixture.CreateClient();
    [Fact]    public async Task CreateOrder_ReturnsCreated_WithValidRequest()    {        // Arrange        var request = new CreateOrderRequest("customer-1", [new("product-1", 2)]);
        // Act        var response = await _client.PostAsJsonAsync("/api/orders", request);
        // Assert        Assert.Equal(HttpStatusCode.Created, response.StatusCode);
        var order = await response.Content.ReadFromJsonAsync<OrderResponse>();        Assert.NotNull(order);        Assert.NotEqual(Guid.Empty, order.Id);        Assert.Contains("/api/orders/", response.Headers.Location?.ToString());    }
    [Fact]    public async Task CreateOrder_ReturnsValidationProblem_WithEmptyItems()    {        // Arrange        var request = new CreateOrderRequest("customer-1", []);
        // Act        var response = await _client.PostAsJsonAsync("/api/orders", request);
        // Assert        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);    }}

Testcontainers for Real Database Testing

csharp
// For SQL Serverprivate readonly MsSqlContainer _mssql = new MsSqlBuilder()    .WithImage("mcr.microsoft.com/mssql/server:2022-latest")    .Build();
// For PostgreSQLprivate readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder()    .WithImage("postgres:18")    .Build();
// For Redisprivate readonly RedisContainer _redis = new RedisBuilder()    .WithImage("redis:7")    .Build();

Verify Snapshot Testing

Use Verify for complex response objects where manual assertions would be fragile.

csharp
[Fact]public async Task GetOrder_MatchesSnapshot(){    // Arrange    await SeedOrder(fixture);
    // Act    var response = await _client.GetAsync("/api/orders/known-id");    var content = await response.Content.ReadAsStringAsync();
    // Assert — compares against a stored .verified.txt file    await Verify(content);}

On first run, Verify creates a .verified.txt file. On subsequent runs, it compares output. If the output changes, the test fails and shows a diff.

Test Data Builders

csharp
public class OrderBuilder{    private string _customerId = "default-customer";    private List<OrderItem> _items = [new("product-1", 1, 9.99m)];    private OrderStatus _status = OrderStatus.Pending;
    public OrderBuilder WithCustomer(string customerId)    {        _customerId = customerId;        return this;    }
    public OrderBuilder WithItems(params OrderItem[] items)    {        _items = [..items];        return this;    }
    public OrderBuilder WithStatus(OrderStatus status)    {        _status = status;        return this;    }
    public Order Build() => Order.Create(_customerId, _items, _status);}
// Usage in testsvar order = new OrderBuilder()    .WithCustomer("vip-customer")    .WithStatus(OrderStatus.Confirmed)    .Build();

Testing Time-Dependent Code

Use TimeProvider (built into .NET 8+) and FakeTimeProvider from Microsoft.Extensions.TimeProvider.Testing.

csharp
[Fact]public async Task ExpireOrders_MarksOldPendingOrdersAsExpired(){    // Arrange    var clock = new FakeTimeProvider(new DateTimeOffset(2025, 6, 1, 0, 0, 0, TimeSpan.Zero));    var db = CreateDb();    var order = Order.Create("customer-1", items, clock.GetUtcNow());    db.Orders.Add(order);    await db.SaveChangesAsync();
    // Advance time past expiry threshold    clock.Advance(TimeSpan.FromDays(31));
    var handler = new ExpireOrders.Handler(db, clock);
    // Act    await handler.Handle(new ExpireOrders.Command(), CancellationToken.None);
    // Assert    var updated = await db.Orders.FindAsync(order.Id);    Assert.Equal(OrderStatus.Expired, updated!.Status);}

Test Naming Convention

Use the pattern: MethodName_StateUnderTest_ExpectedBehavior

csharp
[Fact] public async Task CreateOrder_WithValidItems_ReturnsSuccessResult() { }[Fact] public async Task CreateOrder_WithEmptyItems_ReturnsValidationError() { }[Fact] public async Task GetOrder_WithNonExistentId_ReturnsNotFound() { }[Fact] public async Task CancelOrder_WhenAlreadyShipped_ReturnsConflict() { }

Anti-patterns

Don't Use In-Memory Database for Integration Tests

csharp
// BAD — hides real SQL behavior, transactions, constraintsservices.AddDbContext<AppDbContext>(options =>    options.UseInMemoryDatabase("TestDb"));
// GOOD — Testcontainers with real databaseservices.AddDbContext<AppDbContext>(options =>    options.UseNpgsql(testContainer.GetConnectionString()));

Don't Test Implementation Details

csharp
// BAD — testing that a specific repository method was calledmock.Verify(x => x.AddAsync(It.IsAny<Order>()), Times.Once);mock.Verify(x => x.SaveChangesAsync(), Times.Once);
// GOOD — test the observable outcomevar order = await db.Orders.FindAsync(orderId);Assert.NotNull(order);Assert.Equal(OrderStatus.Created, order.Status);

Don't Share Mutable State Between Tests

csharp
// BAD — static shared stateprivate static readonly AppDbContext SharedDb = CreateDb();
// GOOD — fresh state per test (or use IAsyncLifetime for shared fixtures)private AppDbContext CreateDb() => new(new DbContextOptionsBuilder<AppDbContext>()...);

Don't Write Assertion-Free Tests

csharp
// BAD — no assertion, only checks it doesn't throw[Fact]public async Task CreateOrder_Works(){    await service.CreateAsync(request);    // "it didn't throw, so it works!" — NO}
// GOOD — assert the expected outcome[Fact]public async Task CreateOrder_PersistsOrderToDatabase(){    var result = await service.CreateAsync(request);
    var persisted = await db.Orders.FindAsync(result.Value.Id);    Assert.NotNull(persisted);    Assert.Equal(request.CustomerId, persisted.CustomerId);}

Decision Guide

ScenarioRecommendation
Testing an API endpointWebApplicationFactory integration test
Testing business logic in isolationUnit test with fakes/stubs
Database-dependent testsTestcontainers (real DB)
Complex response validationVerify snapshot testing
Time-dependent logicFakeTimeProvider
External API dependencyWireMock.Net or HttpMessageHandler stub
Parameterized test cases[Theory] with [InlineData] or [MemberData]
Test data setupBuilder pattern
Shared expensive fixtureIClassFixture<T> with IAsyncLifetime

来源与署名

来源：codewithmukesh/dotnet-claude-kit位于skills/testing提交2330089

许可证： 无许可证

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Vertical Slice

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Spec

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