using System;

public class Program

{

    public static void Main()

    {

        ITest test = new Test();

        test.Run();

        ITest overTest = new OverTest();

        overTest.Run();

    }

}

​

public class Test : ITest {

    public virtual void Run(bool test = false) {

        Console.WriteLine(test);

    }

}

​

public class OverTest : Test {

    public override void Run(bool test = true) {

        base.Run(test);

    }

}

​

public interface ITest {

    void Run(bool test = false);

}