public void Section_AddAtPosition()
{
var section = new Section("セクション");
var subsection1 = new Subsection("第一款");
var subsection2 = new Subsection("第二款");
section.Add(subsection1, subsection2);
CollectionAssert.AreEqual(new[] { subsection1, subsection2 }, section.Subsections.ToArray());
var subsection3 = new Subsection("第三款");
section.AddAt(2, subsection3);
CollectionAssert.AreEqual(new[] { subsection1, subsection3, subsection2 }, section.Subsections.ToArray());
}
