integration-test-setup

Integration Test Setup (.NET)

Stand up real integration tests for an ASP.NET Core API: a custom WebApplicationFactory, a real database via Testcontainers, and a sample test that exercises the full HTTP pipeline.

Input — point it at your project

Point this at the API project or repo, not a pasted file — inspect what exists first:

• A project or repo root — find Program.cs, the endpoints, and any existing integration-test project.
• A GitHub URL — clone first, then inspect: git clone --depth 1 <url> /tmp/repo && cd /tmp/repo

Discover the surface yourself before generating, e.g.:

find <target> -name Program.cs | grep -vi "/obj/\|/bin/"
grep -rn "MapGet\|MapPost\|MapPut\|MapDelete\|: ControllerBase\|ICarterModule" --include=*.cs <target> | head
find <target> -iname "*IntegrationTest*" -o -iname "*.IntegrationTests.csproj"

If an integration-test project already exists, review and extend it (e.g. flag EnsureDbCreated vs MigrateAsync, unpinned images, missing state reset) instead of scaffolding from scratch. Pick a representative endpoint to produce the first test.

When this runs

The user wants tests that exercise the app for real — routing, DI, middleware, EF Core against an actual database — not mocked units. Inspect the project, then confirm the database (default PostgreSQL via Testcontainers; support SQL Server) only if you can't infer it from the existing setup.

Packages

dotnet add package Microsoft.AspNetCore.Mvc.Testing
dotnet add package Testcontainers.PostgreSql   # or Testcontainers.MsSql
dotnet add package xunit
dotnet add package FluentAssertions
dotnet add package Respawn                      # reset DB state between tests

The factory (real DB swapped in)

public class IntegrationTestFactory : WebApplicationFactory<Program>, IAsyncLifetime
{
    private readonly PostgreSqlContainer _db = new PostgreSqlBuilder()
        .WithImage("postgres:16-alpine")
        .Build();

    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder.ConfigureTestServices(services =>
        {
            // Remove the app's registered DbContext and point it at the container
            services.RemoveAll<DbContextOptions<AppDbContext>>();
            services.AddDbContext<AppDbContext>(o => o.UseNpgsql(_db.GetConnectionString()));
        });
    }

    public async Task InitializeAsync()
    {
        await _db.StartAsync();
        using var scope = Services.CreateScope();
        var ctx = scope.ServiceProvider.GetRequiredService<AppDbContext>();
        await ctx.Database.MigrateAsync();
    }

    public new async Task DisposeAsync() => await _db.DisposeAsync();
}