Is there a way to parameterize and pass an instance of Startup rather than just the type?

[Tratcher]

From @humblelistener on August 14, 2015 5:8

The intention is to avoid creating a separate TestStartUp class rather - rather inject an instance of Configuration

Sample start up below,

public class Startup
{
  public IConfiguration Configuration {get; set;}

  public void Startup()
  {
    Configuration = new ConfigurationBuilder()
              .AddEnvironmentVariables()
              .Build();
   }

  public void ConfigureServices(IServiceCollection services)
  {
     //uses Configuration object to set up everything
  }
}

In the above implementation, if only

TestServer.CreateBuilder().UseStartup(instanceOfStartup)
is permitted

I can do this,

Startup instanceOfStartup= new Startup();
instanceOfStartup.Configuration = myOwnconfigurationWithKeysRequiredForTest;
//create a test server with 
TestServer.CreateBuilder().UseStartup(instanceOfStartup) 

Advantage: I dont have to maintain multiple startup class.

Does it make sense?

Copied from original issue: dotnet/aspnetcore#831

[Tratcher]

How about the UseStartup(Action<IApplicationBuilder>) overload? So your sample above becomes: TestServer.CreateBuilder().UseStartup(instanceOfStartup.Configure)

[humblelistener]

These overloads are limited - It wont work because

1. Configure method can be using just IApplicationBuilder or taking ILoggerFactory and so on as parameters
2. If I then have a configure services method - it complicates further because the overload pointed out takes a different signature of configureservices compared to the Startup class

Instead of trying to draw two parallels - using StartUp class and StartUpMethods and having supported UseStartUp extension method, IMHO - it will be simple and easy to just start support taking an instance of StartUp thats got environment specific configuration as state in it.

[humblelistener]

and this is what I have to do to keep it working - right now

var startup = new Startup();

//update configuration
startup.Configuration["XYZ_ENV_VAR"] = testEnvValue;

var Action<IApplicationBuilder> configureMethod = (app) => {
  app.UseMvc();
};

var configureServicesStartupMethodInfo = typeof(Startup).GetMethod("ConfigureServices");

var configureServicesMethod = new ConfigureServicesBuilder(configureServicesStartupMethodInfo).Build(startup);

using (var testServer = new TestServer(TestServer.CreateBuilder().UseStartup(configureMethod, configureServicesMethod)))
{
  ...
}

Doesn't feel good! any suggestions?

[HaoK]

Just to clarify the scenario you are trying to accomplish, you mostly want a way to configure a test to run with specific configuration (i.e. just tweak the configuration per test?)

[humblelistener]

that is right, I would prefer to keep the same startup while injecting a different configuration compared to having two startup files or having conditions in the start up file.

[muratg]

Moving this to Backlog as we will be in RC2 ask mode very soon. If you feel strongly about this issue, please ping me.

[davidfowl]

Fixed with 8f5f8d2 which is post RC2. You can add an IStartup class to the DI container and that will get resolved for app startup.

[davidfowl]

PS: it would look like this:

Startup instanceOfStartup= new Startup();
instanceOfStartup.Configuration = myOwnconfigurationWithKeysRequiredForTest;
//create a test server with 
var builder = new WebHostBuilder()
                      .ConfigureServices(services =>
                       {
                            services.AddSingleton<IStartup>(instanceOfStartup);
                       });
var server = new TestServer(builder);

[ohadschn]

And here's a nice blog post about the new IStartup interface: https://www.strathweb.com/2017/06/resolving-asp-net-core-startup-class-from-the-di-container/.