Integration test and hosting ASP.NET Core 6.0 without Startup class

Question

To setup unit tests in previous versions of .NET Core, I could host my web App or web API in a test project the following way:

IHost host = Host.CreateDefaultBuilder()
    .ConfigureWebHostDefaults(config =>
    {
        config.UseStartup<MyWebApp.Startup>();
        config.UseUrls("https://localhost:44331/");
        ...    
    })
    .Build();

The current .NET 6.0 does not use Startup class concept, and thus it could not be referenced. How can host ASP.NET Core apps in a test project in a proper and clean way?

Kilbride

I have a repo showing the use of WebApplicationFactory<T> for unit/integration tests with Minimal APIs, maybe that will help you out: github.com/martincostello/… – Prissy

@martin-costello I see the trick is adding public partial class Program{} – Kilbride

Answer 1

Note that you can switch to generic hosting model (the one using the startup class) if you want.

To set up integration tests with the new minimal hosting model you can make web project internals visible to the test one for example by adding next property to csproj:

<ItemGroup>
  <InternalsVisibleTo Include="YourTestProjectName"/>
</ItemGroup>

And then you can use the Program class generated for the web app in WebApplicationFactory:

class MyWebApplication : WebApplicationFactory<Program>
{
    protected override IHost CreateHost(IHostBuilder builder)
    {
        // shared extra set up goes here
        return base.CreateHost(builder);
    }
}

And then in the test:

var application = new MyWebApplication();
var client = application.CreateClient();
var response = await client.GetStringAsync("/api/WeatherForecast");

Or use WebApplicationFactory<Program> from the test directly:

var application = new WebApplicationFactory<Program>()
    .WithWebHostBuilder(builder =>
    {
        builder.ConfigureServices(services =>
        {
           // set up servises
        });
    });
var client = application.CreateClient();
var response = await client.GetStringAsync("/api/WeatherForecast");

Or instead of using InternalsVisibleTo you can declare public partial Program class and use it. For example add next to the bottom of top-level statement file (the rest is the same):

public partial class Program { }

Code examples from migration guide.

Imogeneimojean

Any idea on how to do this without using WebApplicationFactory or TestServer? Asking as I'm trying to implement PactNet provider tests, and have yet to figure this out github.com/pact-foundation/pact-net – Derek

@ImerMuhović did you ever get this solved for Pact? – Valiancy

@Valiancy you can try looking into options listed here – Imogeneimojean

@GuruStron Thank you! putting public partial class Program { } and the class MyWebApplication : WebApplicationFactory<Program> worked for me – Silvas