blog.stevanfreeborn.com/test/Blog.Tests/EndToEnd/BlogHostFactory.cs

using Blog.Posts;

using Microsoft.AspNetCore.Hosting.Server.Features;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.TestHost;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Blog.Tests.EndToEnd;

public class BlogHostFactory<TProgram> : WebApplicationFactory<TProgram> where TProgram : class
{
  private IHost? _host;

  private void EnsureServer()
  {
    if (_host is null)
    {
      using var _ = CreateDefaultClient();
    }
  }

  protected override void Dispose(bool disposing)
  {
    _host?.Dispose();
  }

  public string ServerAddress
  {
    get
    {
      EnsureServer();
      return ClientOptions.BaseAddress.ToString();
    }
  }

  protected override IHost CreateHost(IHostBuilder builder)
  {
    var testHost = builder
      .ConfigureWebHost(webHostBuilder =>
      {
        webHostBuilder.ConfigureLogging(config => config.ClearProviders());
        webHostBuilder.ConfigureTestServices(services =>
        {
          var postsDirectory = Path.Combine(Directory.GetCurrentDirectory(), "TestPosts");
          var postServiceOptions = new FilePostServiceOptions() { PostsDirectory = postsDirectory };
          services.AddSingleton(Options.Create(postServiceOptions));
        });
      })
      .Build();

    builder.ConfigureWebHost(
      webHostBuilder => webHostBuilder.UseKestrel(
        o => o.Listen(IPAddress.Loopback, 0)
      )
    );

    _host = builder.Build();
    _host.Start();

    var server = _host.Services.GetRequiredService<IServer>();
    var addresses = server.Features.GetRequiredFeature<IServerAddressesFeature>();

    ClientOptions.BaseAddress = addresses.Addresses
      .Select(x => new Uri(x))
      .Last();

    testHost.Start();
    return testHost;
  }
}