.NET 10.0 integration tests error with xunit v3 assembly fixture and WebApplicationFactory

Question

When setting up an integration test with the .NET 10.0 SDK and the new xunit v3, I get the following error when trying to customize the WebApplicationFactory:

System.InvalidOperationException: The server has not been started or no web application was configured.

I am using Microsoft.AspNetCore.Mvc.Testing v10.0.0 with the assembly fixture feature of xunit v3

[assembly: AssemblyFixture(typeof(ApiFactory))]
namespace WebApi.Tests.Integration.Fixtures;

public class ApiFactory : WebApplicationFactory<WebApi.Startup>, IAsyncLifetime
{
    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        builder.ConfigureServices(services =>
        {
            var descriptor =
                services.SingleOrDefault(x => x.ServiceType == typeof(DbContextOptions<DbContext>));

            if (descriptor != null)
            {
                services.Remove(descriptor);
            }

            services.AddDbContext<DbContext>(options
                => options.UseSqlServer("Server=.;Database=Database;Trusted_Connection=True;"));

            services.AddHttpClient("Api", client =>
            {
                client.BaseAddress = new Uri("http://localhost/api/v1/");
            });
        });
    }

    public async ValueTask InitializeAsync()
    {
    }

    public new async Task DisposeAsync()
    {
        await base.DisposeAsync();
    }
}

I have a simple integration test that will call the health check endpoint and check for a 200 response.

public class HealthCheckTests
{
    private readonly HttpClient _client;

    public HealthCheckTests(ApiFactory factory)
    {
        _client = factory.CreateClient();
    }

    [Fact]
    public async Task Heath_Check_Success_Test()
    {
        // arrange

        // act
        var response = await _client.GetAsync("healthcheck", TestContext.Current.CancellationToken);

        // assert
        response.StatusCode.Should().Be(HttpStatusCode.OK);
    }
}

The problem comes when overriding the ConfigureWebHost method. When doing so I get the error:

System.InvalidOperationException: The server has not been started or no web application was configured.

If I comment out the override the test will succeed but I wont be able to customize the WebApplicationFactory for my testing needs.

Edit

Please see the stack trace below.

System.InvalidOperationException: The server has not been started or no web application was configured. at Microsoft.AspNetCore.TestHost.TestServer.get_Application() at Microsoft.AspNetCore.TestHost.TestServer.CreateHandler() at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory1.CreateHandler() at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory1.CreateDefaultClient(DelegatingHandler[] handlers) at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory1.CreateDefaultClient(Uri baseAddress, DelegatingHandler[] handlers) at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory1.CreateClient(WebApplicationFactoryClientOptions options) at Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory1.CreateClient() at CampaignService.WebApi.Tests.Integration.Tests.HealthCheckTests..ctor(ApiFactory factory) in C:\WebApi.Tests.Integration\Tests\HealthCheckTests.cs:line 14 at InvokeStub_HealthCheckTests..ctor(Object, Span1) at System.Reflection.MethodBaseInvoker.InvokeWithOneArg(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)

Can you add the full information from the exception including stack trace and any inner exceptions? — user700390
– user700390, Commented 7 hours ago
Can you please post a full minimal reproducible example somewhere (for example @github) for lazy person like me? — Guru Stron
– Guru Stron, Commented 5 hours ago

user700390 · Accepted Answer · 2025-12-01 18:50:27Z

2

It looks like you are not calling base.ConfigureWebHost() in your method override on the subclass. I think this is the most likely culprit here.

answered 7 hours ago

user700390

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1 Comment

Dblock247 6 hours ago

I am sorry I should have mentioned that I have called that both before and after the custom setup with the same error message.

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