Домашнее задание по тестированию.

Hometask.cs

using System;

namespace Hometask
{
    public class UserRegistrationService
    {
        public void RegisterUser(string emailAddress)
        {
            if(client.CheckUserExists(emailAddress))
                throw new Exception(string.Format("User with e-mail '{0}' already exists", emailAddress));
            client.CreateUser(emailAddress);
            var userInfo = client.GetUserInfo(emailAddress);
            emailSendingService.SendEmail(emailBuilder.BuildAuthenticationEmailInfo(userInfo));
        }

        private readonly MySqlDatabaseClient client = new MySqlDatabaseClient();
        private readonly EmailMessageBuilder emailBuilder = new EmailMessageBuilder();
        private readonly EmailSendingService emailSendingService = new EmailSendingService();
    }

    internal class EmailMessageBuilder
    {
        public EmailMessageInfo BuildAuthenticationEmailInfo(UserInfo userInfo)
        {
            return new EmailMessageInfo
            {
                EmailAddress = userInfo.Login,
                Subject = "You have been registered on ZZZ.com",
                Body = string.Format("Login: {0}\nPassword: {1}", userInfo.Login, userInfo.Password),
            };
        }
    }

    internal class EmailSendingService
    {
        //Этот класс посылает электронные письма

        public void SendEmail(EmailMessageInfo emailMessageInfo)
        {
            throw new NotImplementedException();
        }
    }

    internal class MySqlDatabaseClient
    {
        //Этот класс инкапсулирует запросы к реальной базе данных

        public bool CheckUserExists(string login)
        {
            throw new NotImplementedException();
        }

        public void CreateUser(string login)
        {
            throw new NotImplementedException();
        }

        public UserInfo GetUserInfo(string login)
        {
            throw new NotImplementedException();
        }
    }

    internal class UserInfo
    {
        public string Login { get; set; }
        public string Password { get; set; }
    }

    internal class EmailMessageInfo
    {
        public string EmailAddress { get; set; }

        public string Subject { get; set; }

        public string Body { get; set; }
    }
}