Testing .NET 6 Applications: Integration Testing with WebApplicationFactory

Unit tests are not enough. Integration tests verify your app works end-to-end, including middleware, dependency injection, and database logic. `WebApplicationFactory` spins up an in-memory test host.

Setup

public class IntegrationTest : IClassFixture<WebApplicationFactory<Program>>
{
    private readonly HttpClient _client;

    public IntegrationTest(WebApplicationFactory<Program> factory)
    {
        _client = factory.CreateClient();
    }

    [Fact]
    public async Task Get_ReturnsSuccess()
    {
        var response = await _client.GetAsync("/api/todos");
        response.EnsureSuccessStatusCode();
    }
}

Customizing Services

Replace the real database with an in-memory one.

factory.WithWebHostBuilder(builder =>
{
    builder.ConfigureServices(services =>
    {
        services.RemoveAll<DbContextOptions<MyDbContext>>();
        services.AddDbContext<MyDbContext>(opt => opt.UseInMemoryDatabase("Test"));
    });
});

Key Takeaways

• Use **Testcontainers** (covered earlier) for real SQL testing.
• Check HTTP status codes, response bodies, and headers.