WebApplicationFactory<TEntryPoint> will not allow Middleware to be added via the ConfigureWebHost() method and maintain the existing functionality from the TEntryPoint.

[simkin2004]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When attempting to use a CustomWebApplicationFactory, I wanted to add a Middleware to set some specific values to handle underlying HttpContext.
Started with this code returning a 200 - OK

    public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup : class
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {          
            base.ConfigureWebHost(builder);
        }
    }

I tried to jump to the simple middleware to ensure this would work with this code and it returned a 404 - Not Found

    public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup : class
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            
            builder.Configure(app => 
                        {
                            app.Use(async (ctx, next) => { await next(ctx); });

                        });
            base.ConfigureWebHost(builder);
        }
    }

Someone in discussions suggested that I didn't need to pass the context, so i tried this code and it returned a 404 - Not Found

    public class CustomWebApplicationFactory<TStartup> : WebApplicationFactory<TStartup> where TStartup : class
    {
        protected override void ConfigureWebHost(IWebHostBuilder builder)
        {
            
            builder.Configure(app => 
                        {
                            app.Use(async (ctx, next) => { await next(); });

                        });
            base.ConfigureWebHost(builder);
        }
    }

Ultimately, I tried to do a "No Operation" call to see if my code was breaking it; this code returned a 404 - Not Found.

    protected override void ConfigureWebHost(IWebHostBuilder builder)
    {
        
        builder.Configure(app => 
                    {
                        // no op
                    });
        base.ConfigureWebHost(builder);
    }
}

Expected Behavior

Expected behavior is that the middleware configurations above would operate and return a 200 - OK by relying on the configuration provided by the TEntryPoint.

Steps To Reproduce

simple sample project provided by #53999

Additional troubleshooting in the discussion and documented above.

Exceptions (if any)

No response

.NET Version

8.0.302

Anything else?

No response

[simkin2004]

This potential workaround exhibits the same behavior both with sending the HttpContext (ctx) and not sending it.
Sending the HttpContext (ctx) example is below

var waf = new WebApplicationFactory<Program>()
                        .WithWebHostBuilder(builder =>
                        {
                            builder.Configure(app =>
                            {
                                app.Use(async (ctx, next) => { await next(ctx); });
                            });  
                        });