‫جلوگیری از افشای حالت خصوصی در تست‌های واحد

public class Member
{
    private MembershipLevel _level = MembershipLevel.Standard;

    public void Upgrade()
    {
        _level = MembershipLevel.Premium;
    }

    public decimal GetDiscount()
    {
        return _level == MembershipLevel.Premium ? 0.1m : 0m;
    }
}

public enum MembershipLevel
{
    Standard,
    Premium
}

[Fact]
public void New_Member_Should_Have_No_Discount()
{
    var member = new Member();
    Assert.Equal(0m, member.GetDiscount());
}

[Fact]
public void Upgraded_Member_Should_Get_10_Percent_Discount()
{
    var member = new Member();
    member.Upgrade();
    Assert.Equal(0.1m, member.GetDiscount());
}

public class DiscountCalculator
{
    public decimal Calculate(MembershipLevel level)
    {
        return level == MembershipLevel.Premium ? 0.1m : 0m;
    }
}

public class Member
{
    private MembershipLevel _level = MembershipLevel.Standard;
    private readonly DiscountCalculator _calculator;

    public Member(DiscountCalculator calculator)
    {
        _calculator = calculator;
    }

    public void Upgrade()
    {
        _level = MembershipLevel.Premium;
    }

    public decimal GetDiscount()
    {
        return _calculator.Calculate(_level);
    }
}