arleypadua

        // We also want to encapsulate the way this class is instantiated.
        private Order() { }

        public string OrderId { get; private set; }
        public string CustomerId { get; private set; }
        public decimal Discount { get; private set; }
        public bool Paid { get; private set; }
        public DateTime? PaymentTime { get; private set; }
        public DateTime CreationTime { get; private set; }
        public List<OrderItem> Items { get; private set; }

arleypadua

    public class Order
    {
        public string OrderId { get; set; }
        public string CustomerId { get; set; }
        public decimal Discount { get; set; }
        public bool Paid { get; set; }
        public DateTime? PaymentTime { get; set; }
        public DateTime CreationTime { get; set; }
        public List<OrderItem> Items { get; set; }

arleypadua

    public class OrderService
    {
        private readonly IOrderRepository _repository;
        public void AddItem(string orderId, OrderItem item)
        {
            var order = _repository.GetById(orderId);

            // Validate
            if (order.Paid) throw new InvalidOperationException("The order is paid already.");
            if (order.Items.Count > 5) throw new InvalidOperationException("Cannot add more than 5 items in an order.");

arleypadua

    public class Order
    {
        public string OrderId { get; set; }
        public string CustomerId { get; set; }
        public decimal Discount { get; set; }
        public bool Paid { get; set; }
        public DateTime? PaymentTime { get; set; }
        public DateTime CreationTime { get; set; }
        public List<OrderItem> Items { get; set; }

arleypadua

var builder = new EmployeeTestBuilder();

var employee = builder
    .WithName("Samuel")
    .HasAge(35)
    .HasGrossSalaryOf(1000)
    .Build();

employee.CalculateNetSalary().Should().Be(850);

arleypadua

public class EmployeeTestBuilder
{
    private Employee _employee;
    public EmployeeTestBuilder()
    {
        _employee = new Employee();
    }

    public EmployeeTestBuilder Default()
    {

arleypadua

public class Employee
{
    public string Name { get; set; }
    public DateTime BirthDate { get; set; }
    public double GrossSalary { get; set; }

    public double CalculateNetSalary()
    {
        var age = DateTime.Now.Year - BirthDate.Year;