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()); }