using System;

​

public interface IOrderRepository { }

​

public class Order { }

​

public class Program

{

    public static void Main()

    {

        IOrderRepository sqlOrderRepository = new SqlOrderRepository();

        OrderService sqlOrderService = new OrderService(sqlOrderRepository);

        sqlOrderService.ProcessOrder(new Order());

        Console.WriteLine("Order processed");

​

        IOrderRepository mockOrderRepository = new MockOrderRepository();

        MockOrderService mockOrderService = new MockOrderService(mockOrderRepository);

        mockOrderService.ProcessOrder(new Order());

        Console.WriteLine("Order processed (Mock)");

    }

}

​

public class OrderService

{

    private readonly IOrderRepository _orderRepository;

​

    public OrderService(IOrderRepository orderRepository)

    {

        _orderRepository = orderRepository;

    }

​

    public void ProcessOrder(Order order) { }

}

​

public class MockOrderService

{

    private readonly IOrderRepository _orderRepository;

​

    public MockOrderService(IOrderRepository orderRepository)

    {

        _orderRepository = orderRepository;

    }

​

    public void ProcessOrder(Order order) { }

}

​

public class SqlOrderRepository : IOrderRepository { }

​

public class MockOrderRepository : IOrderRepository { }