UserRegistration.cs

public class UserRegistration
{
private static int _testCount = 0;
private readonly UsernameReservationSync _reservation;
private readonly IUserRepository _repository;

public UserRegistration(UsernameReservationSync reservation, IUserRepository repository)
{
    _reservation = reservation;
    _repository = repository;
}

public bool Register(string username)
{
    if (_reservation.Reserve(username) == false)
    {
        return false;
    }

    // For testing to show the expiry
    if (username == "test" && _testCount == 0)
    {
        _testCount++;
        return false;
    }

    var account = new Account(username);
    _repository.Add(account);
    _repository.Save();

    if (_reservation.Complete(username) == false)
    {
        _repository.Remove(account);
        return false;
    }

    return true;
}