using System;

public class Program

{

}

​

public class AppExtensions 

{

    public static void AddSomething(this IAppBuilder builder)

    {

        builder.GetService<MyService>().Start();

    }

}

​

...

public class MyService()

{

    ...

    private void TimerService;

    public MyService()

    {

        // setup fields

        TimerService = new TimerService()...

    }

    public void Start()

    {

        TimerService.Start();

    }        

}

​

​

public class MyServiceMock()

{

    public void Start()

    {

        Counter.Counter+=1;

    }        

}

​

​

public class AppBuilderMock{

    public T GetService<T>(){

        return default(T);

    }

}

​

​

public static Counter{

    public static int Counter{get; set;}

}

​

public void Test(){

    var builder = new AppBuilderMock();

    AppBuilderMock.AddSomething();

}

​

​

​

​

​

​

​

​

​