09. 非公開メソッドの入れ替え で解説するテスト対象 DTO 群。こんな感じで設計されていれば・・・。

09_10.cs

...(snip)...

public class ULColumns : IEnumerable
{
    List<ULColumn> m_columns = new List<ULColumn>();
    IValidation<ULColumns> m_val;

    public ULColumns(IValidation<ULColumns> val)
    {
        if (val == null)
            throw new ArgumentNullException("val");

        m_val = val;
    }

    public void Add(ULColumn column)
    {
        m_val.Validate(this);
        m_columns.Add(column);
    }

    public void Remove(ULColumn column)
    {
        m_val.Validate(this);
        m_columns.Remove(column);
    }

    ...(snip)...

    internal static IValidation<ULColumns> GetDefaultValidation(ULTableStatus status)
    {
        return new ColumnsVariabilityValidator(status);
    }

    class ColumnsVariabilityValidator : IValidation<ULColumns>
    {
        readonly ULTableStatus m_status;

        public ColumnsVariabilityValidator(ULTableStatus status)
        {
            m_status = status;
        }

        public void Validate(ULColumns t)
        {
            if (!m_status.IsOpened)
                throw new InvalidOperationException("The column can not be modified because owner table has not been opened.");

            if (0 < m_status.RowsCount)
                throw new ArgumentException("The column can not be modified because some rows already exist.");
        }
    }
}

public class ULTable
{
    ULTableStatus m_status = new ULTableStatus();

    public ULTable(string tableName)
    {
        TableName = tableName;
    }

    ...(snip)...

    ULColumns m_columns;
    public virtual ULColumns Columns
    {
        get
        {
            if (m_columns == null)
                m_columns = new ULColumns(ULColumns.GetDefaultValidation(m_status));
            return m_columns;
        }
    }

    ...(snip)...
}

public interface IValidation<T>
{
    void Validate(T obj);
}