public static void Main()
{
    var stub = new StubActor(2);
    var logic = new SomeLogic(stub);

    var actualResult = logic.CalculateResult();
    var expectedResult = 8;

    Assert.Equals(actualResult, expectedResult);
}


public interface IActor
{
    Int32 Act();
}
public class StubActor: IActor
{
    private readonly Int32 result;
    public StubActor(Int32 result)
    {
        this.result = result;
    }
    public Int32 Act()
    {
        return result;
    }
}
public class RealActor: IActor
{
    private IActorService actorService;
    public RealActor (IActorService)
    {
        this.actorService = actorService;
    }

    public Int32 Act()
    {
        return actorService.GetData();
    }
}

public class SomeLogic
{
    private IActor actor;
    public SomeLogic(IActor actor)
    {
        this.actor = actor;
    }

    public Int32 CalculateResult()
    {
        return (2 + actor.Act()) * 2;
    }
}