using System;

public class Program

{

    public static void Main()

    {

        ITest t = new Test();

        Console.WriteLine(t.OnConsuming());

    }

}

​

public class Test : AbstractTest

{

    public string OnConsuming() =>  "Should be this";

}

​

public abstract class AbstractTest :  ITest

{

}

​

public interface ITest

{

    public string OnConsuming() => "Should ******NOT***** be this";

}

​