단위 테스트 - 7장 가치 있는 단위 테스트를 위한 리팩터링

1. CRM 시스템의 초기 구현

public class User
{
    public int UserId { get; private set;}
    public string Email { get; private set; }
    public UserType Type { get; private set; }
    
    public void ChangeEmail(int userId, string newEmail)
    {
        object[] data = Database.GetUserById(userId);
        UserId = userId,
        Email = (string)data[1];
        Type = (UserType)data[2];
        
        if (Email == newEamil)
            return;
            
        object[] companyData = Database.GetCompany();
        string companyDomainName = (string)companyData[0];
        int numberOfEmployees = (int)companyData[1];
        
        string emailDomain = newEmail.Split("@")[1];
        bool isEmailCorporate = emailDomain == companyDomainName;
        UserType newType = isEmailCorporate
            ? UserType.Employee
            : UserType.Customer;
            
        if (Type != newType) {
            int delta = newType == UserType.Employee ? 1 : -1;
            int newNumber = numberOfEmployees + delta;
            Database.SaveCompany(newNumber);
        }
        
        Email = newEmail;
        Type = newType;
        
        Database.SaveUser(this);
        MessageBus.SendEmailChangedMEssage(userId, newEmail);
    }
}

public enum UserType
{
    Customer = 1,
    Employee = 2
}

2-1. User의 ChangeEmail 메소드 업데이트

// UserController : Line #17 에서 호출되는 부분 
public int ChangeEmail(string newEmail, string companyDomainName, int numberOfEmployees)
{
    if(Email == newEmail)
        return numberOfEmployees;

    string emailDomain = newEmail.Split("@")[1];
    bool isEmailCorporate = emailDomain == companyDomainName;
    UserType newType = isEmailCorporate
        ? UserType.Employee
        : UserType.Customer;

    if (Type != newType)
    {
        int delta = newType == UserType.Employee ? 1 : -1;
        int newNumber = numberOfEmployees + delta;
        Database.SaveCompany(newNumber);
    }

    Email = newEmail;
    Type = newType;

    return numberOfEmployees;
}

2-2. UserFactory Class

public class UserFactory
{
    public static User Create(object[] data)
    {
        Precondition.Requires(data.Length >= 3);
        
        int id = (int)data[0];
        string email = (string)data[1];
        UserType type = (UserType)data[2];
        
        return new User(id, email, type);
    }
}

2-3. new Company Class

public class Company
{
    public string DomainName { get; private set; }
    public int NumberOfEmployees { get; private set; }
    
    public void ChangeNumberOfEmployees(int delta)
    {
        Precondition.Requires(NumberOfEmployees + delta >= 0);
        NumberOfEmployees += delta;
    }
    
    public bool IsEmailCorporate(string email)
    {
        string emailDomain = email.Split('@')[1];
        return emailDomain == DomainName;
    }
}

2-4. 애플리케이션 서비스, 버전 2

public class UserController
{
    private readonly Database _database = new Database();
    private readonly MessageBus _messageBus = new MessageBus();
    
    public void ChangeEmail(int userId, string newEmail)
    {
        object[] userData = _database.GetUserById(userId);
        User user = UserFactory.Create(userData);
        
        object[] companyData = _database.GetCompany();
        Company company = CompanyFactory.Create(companyData);
        
        user.ChangeEmail(newEmail, company);
                    
        _database.SaveCompany(company);
        _database.SaveUser(user);
        _messageBus.SendEmailChangedMEssage(userId, newEmail);
    }
}

2-5. User Class, version 2

public class User
{
    public int UserId { get; private set;}
    public string Email { get; private set; }
    public UserType Type { get; private set; }
    
    public void ChangeEmail(string newEmail, Company company)
    {
        if (Email == newEamil)
            return;

        UserType newType = company.isEmailCorporate(newEmail)
            ? UserType.Employee
            : UserType.Customer;
            
        if (Type != newType)
        {
            int delta = newType == UserType.Employee ? 1 : -1;
            int newNumber = numberOfEmployees + delta;
            Database.SaveCompany(newNumber);
        }
        
        Email = newEmail;
        Type = newType;        
    }
}

2. 애플리케이션 서비스, 버전 1

public class UserController
{
    private readonly Database _database = new Database();
    private readonly MessageBus _messageBus = new MessageBus();
    
    public void ChangeEmail(int userId, string newEmail)
    {
        object[] data = _database.GetUserById(userId);
        string email = (string)data[1];
        UserType type = (UserType)data[2];
        var user = new User(userId, email, type);
        
        object[] companyData = _database.GetCompany();
        string companyDomainName = (string)companyData[0];
        int numberOfEmployees = (int)companyData[1];
        
        int newNumberOIfEmployees = user.ChangeEmail(newEmail, companyDomainName, numberOfEmployees);
                    
        _database.SaveCompany(newNumberOIfEmployees);
        _database.SaveUser(user);
        _messageBus.SendEmailChangedMEssage(userId, newEmail);
    }
}

3-1. Test code of User class

[Fact]
public void Changing_email_from_non_corporate_to_corporate()
{
    var company = new Company("mycorp.com", 1);
    var sut = new User(1, "user@gmail.com", UserType.Customer);
    
    sut.ChangeEmail("new@mycorp.com", company);
    
    Assert.Equal(2, company.NumberOfEmployees);
    Assert.Equal("new@mycorp.com", sut.Email);
    Assert.Equal(UserType.Employee, sut.Type);
}

3-2. Test code of User class using arguments

[InlineData("mycorp.com", "email@mycorp.com", true)]
[InlineData("mycorp.com", "email@gmail.com", false)]
[Theory]
public void Differentiates_a_corporate_email_from_non_corporate(
    string domain, string email, bool expectedResult)
{
    var sut = new Company(domain, 0);
    
    bool isEmailCorporate = sut.IsEmailCorporate(email);
    
    Assert.Equal(expectedResult, isEmailCorporate);
}

4-1 CanExecute-Execute example

public string CanChangeEmail()
{
    if (IsEmailConfirmed) {
        return "Can't change a confirmed email";
    }
    return null;
}

public void ChangeEmail(string newEmail, Company company)
{
    Precondition.Requires(CanChangeEmail() == null);
    
    /* TODO */
}

4-2-1 EmailChangedEvent

public class EmailChanedEvent
{
    public int UserID { get; }
    public string NewEmail { get; }
}

4-2-2 User ChangeEmail with EmailChangedEvent

public void ChangeEmail(string newEmail, Company company)
{
    Precondition.Requires(CanChangeEmail() == null);
    
    if (Email == newEmail)
        return;
    
    UserType newType = company.isEmailCorporate(newEmail)
        ? UserType.Employee
        : UserType.Customer;
        
    if (Type != newType)
    {
        int delta = newType == UserType.Employee ? 1 : -1;
        company.ChangeNumberOfEmployees(delta);
    }
    
    Email = newEmail;
    Type = newType;
    EmailChangedEvents.Add(new EmailChangedEvent(UserId, newEmail));
}

4-2-3 Contoller ChangeEmail with EmailChangedEvent

public string ChangedEmail(int userId, string newEmail)
{
    object[] userData = _database.GetUserById(userId);
    User user = UserFactory.Create(userData);
    
    string error = user.CanChangeEmail();
    if (error != null)
        return error;
    
    object[] companyData = _database.getCompany();
    Company company = CompanyFactory.Create(companyData);
    
    user.ChangeEmail(newEmail, company);
    
    _database.SaveCompany(company);
    _database.SaveUser(user);
    foreach (var ev in user.EmailChangedEvents) {
        _messageBus.SendEmailChangedMessage(
            ev.UserId, ev.NewEmail);
    }
    
    return "OK";
}

4-2-4 Domain Unit Test with Domain Event

[Fact]
public void Changing_email_from_corporate_to_non_corporate()
{
    var company = new Company("mycorp.com", 1)
    var sut = new User(1, "user@mycorp.com", UserType.Employee, false);
    
    sut.ChangeMail("new@gmail.com", company);
    
    company.NumberOfEmployees.Should().Be(0);
    sut.Email.Should().Be("new@gmail.com");
    sut.Type.Should().Be(UserType.Customer);
    sut.EmailChangedEvents.Should().Equal(new EmailChangedEvent(1, "new@gmail.com"));
}