Writing testable code

Writing testable code in C# is essential for ensuring that code behaves as expected and can be efficiently tested with automated tests. Here are some C#-specific tips and examples for writing testable code:

1. Use interfaces to define dependencies: Interfaces are a powerful tool for defining dependencies between classes. By defining dependencies through interfaces, it is easy to swap out dependencies with test doubles, such as mocks or stubs, for testing purposes. For example, consider the following code:

   public class OrderService{    private readonly IorderRepository _orderRepository;    public OrderService(IorderRepository orderRepository)    {        _orderRepository = orderRepository;    }    public Order GetOrderById(int id)    {        return _orderRepository...