# Blazor Testing ## Test Project Setup ```bash dotnet new xunit -n MyApp.Tests dotnet add MyApp.Tests package bunit dotnet add MyApp.Tests package FluentAssertions dotnet add MyApp.Tests package NSubstitute dotnet add MyApp.Tests package Microsoft.AspNetCore.Mvc.Testing dotnet add MyApp.Tests package Testcontainers.PostgreSql # For real DB tests ``` ## bUnit Component Tests ```csharp public sealed class CounterTests : TestContext { [Fact] public void Counter_StartsAtZero() { var cut = RenderComponent(); cut.Find("p").TextContent.Should().Contain("0"); } [Fact] public void Counter_IncrementsOnClick() { var cut = RenderComponent(); cut.Find("button").Click(); cut.Find("p").TextContent.Should().Contain("1"); } } ``` ### Testing with Parameters and Services ```csharp public sealed class ProductListTests : TestContext { [Fact] public async Task Should_Display_Products() { var mockService = Substitute.For(); mockService.GetAllAsync(Arg.Any()) .Returns(new List { new(1, "Widget", 9.99m), new(2, "Gadget", 19.99m) }); Services.AddSingleton(mockService); var cut = RenderComponent(); cut.WaitForState(() => cut.FindAll(".product-card").Count > 0); cut.FindAll(".product-card").Should().HaveCount(2); cut.Markup.Should().Contain("Widget"); } } ``` ### Testing Forms ```csharp [Fact] public void Form_Validates_Required_Fields() { var cut = RenderComponent(); cut.Find("form").Submit(); cut.FindAll(".validation-message").Should().NotBeEmpty(); } [Fact] public void Form_Submits_Valid_Data() { var mockService = Substitute.For(); Services.AddSingleton(mockService); var cut = RenderComponent(); cut.Find("#name").Change("New Product"); cut.Find("#price").Change("29.99"); cut.Find("form").Submit(); mockService.Received(1).CreateAsync( Arg.Is(r => r.Name == "New Product"), Arg.Any()); } ``` ## API Integration Tests ```csharp public sealed class ProductApiTests : IClassFixture> { private readonly HttpClient _client; public ProductApiTests(WebApplicationFactory factory) { _client = factory.WithWebHostBuilder(builder => { builder.ConfigureServices(services => { services.RemoveAll(); services.AddDbContext(opts => opts.UseInMemoryDatabase($"Test-{Guid.NewGuid()}")); }); }).CreateClient(); } [Fact] public async Task GetProducts_ReturnsOk() { var response = await _client.GetAsync("/api/products"); response.StatusCode.Should().Be(HttpStatusCode.OK); } [Theory] [InlineData("", HttpStatusCode.BadRequest)] [InlineData("Valid Name", HttpStatusCode.Created)] public async Task CreateProduct_ValidatesInput(string name, HttpStatusCode expected) { var response = await _client.PostAsJsonAsync("/api/products", new { Name = name, Price = 10.0 }); response.StatusCode.Should().Be(expected); } } ``` ## Test with Real Database (Testcontainers) ```csharp public sealed class ProductDbTests : IAsyncLifetime { private readonly PostgreSqlContainer _postgres = new PostgreSqlBuilder() .WithImage("postgres:16") .Build(); public async Task InitializeAsync() => await _postgres.StartAsync(); public async Task DisposeAsync() => await _postgres.DisposeAsync(); [Fact] public async Task Can_Create_And_Read_Product() { var options = new DbContextOptionsBuilder() .UseNpgsql(_postgres.GetConnectionString()) .Options; await using var db = new AppDbContext(options); await db.Database.EnsureCreatedAsync(); db.Products.Add(new Product { Name = "Test", Price = 9.99m }); await db.SaveChangesAsync(); var product = await db.Products.FirstAsync(); product.Name.Should().Be("Test"); } } ``` ---