csharp-testing

# C# Testing Patterns Comprehensive testing patterns for .NET applications using xUnit, FluentAssertions, and modern testing practices. ## When to Activate - Writing new tests for C# code - Reviewing test quality and coverage - Setting up test infrastructure for .NET projects - Debugging flaky or slow tests ## Test Framework Stack | 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 | ## Unit Test Structure ### Arrange-Act-Assert ```csharp 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); ...