.NET Core TestServer returning 404 when using Startup class defined in unit test project

Question

I've a basic .net core api web app and a unit test project that uses a TestServer to make http requests.

I've a TestStartup class that subclassed the Startup class in the api project.

If the Startup class is in the unit test project i get a 404 response. If the TestStartup class is moved to the api project i get a 200 reponse.

Api Project

Api.csproj

<PackageReference Include="Microsoft.AspNetCore.App" />

Program.cs

public class Program
{
    public static void Main(string[] args)
    {
        CreateWebHostBuilder(args).Build().Run();
    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>();
}

Startup.cs

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvcCore();
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        app.UseMvc();
    }
}

TestController.cs

public class TestController : ControllerBase
{
    [HttpGet("test")]
    public ObjectResult Get()
    {
        return Ok("data");
    }
}

Unit Test Project

Tests.csproj

<PackageReference Include="Microsoft.AspNetCore.App" Version="2.1.1" />
<PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="2.1.2" />
<PackageReference Include="Microsoft.AspNetCore.TestHost" Version="2.1.1" />
<PackageReference Include="Microsoft.Extensions.PlatformAbstractions" Version="1.1.0" />
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.8.0" />
<PackageReference Include="NUnit" Version="3.10.1" />
<PackageReference Include="NUnit3TestAdapter" Version="3.10.0" />

Tests.cs

[TestFixture]
public class Tests
{
    [Test]
    public async Task Test()
    {
        var server = new TestServer(WebHost.CreateDefaultBuilder()
            .UseStartup<TestStartup>()
            .UseEnvironment("Development"));

        var response = await server.CreateClient().GetAsync("test");
    }
}

Startup.cs

public class TestStartup : Startup
{ }

Answer 1

In case someone experiences this targeting ASP.NET Core 3.0 or 3.1, don't forget to change the test project SDK to Microsoft.NET.Sdk.Web, i.e.

<Project Sdk="Microsoft.NET.Sdk.Web">

as per Test app prerequisites.

Answer 2

You could try two options below:

• Add AddApplicationPart to Startup.cs

  namespace IntegrationTestMVC
  {
  public class Startup
  {         
  
      // This method gets called by the runtime. Use this method to add services to the container.
      public void ConfigureServices(IServiceCollection services)
      {   
         services.AddMvc().AddApplicationPart(Assembly.Load(new AssemblyName("IntegrationTestMVC"))); //"IntegrationTestMVC" is your original project name
      }
  

• Try to convert TestFixture to IClassFixture

      public class IntegrationTestMVCUnitTest : IClassFixture<WebApplicationFactory<TestStartup>>
  {
      private readonly HttpClient _client;
      private readonly WebApplicationFactory<TestStartup> _factory;
  
      public IntegrationTestMVCUnitTest(WebApplicationFactory<TestStartup> factory)
      {
  
          _factory = factory;
          _client = factory.CreateClient();
      }
  
      [Fact]
      public async Task IndexRendersCorrectTitle()
      {
          var response = await _client.GetAsync(@"/test");
      }
  
  }
  

For the second option, you could refer Integration tests in ASP.NET Core