public void AddSumNode() { var xmlDoc = new XmlDocument(TestUtility.CreateDefaultNSM().NameTable); xmlDoc.LoadXml( $@"<rowItems xmlns=""http://schemas.openxmlformats.org/spreadsheetml/2006/main"" count=""3""> <i> <x v=""1""/> </i> <i r=""1""> <x v=""2""/> </i> <i r=""1""> <x v=""3""/> </i> </rowItems>" ); var node = xmlDoc.FirstChild; var itemsCollection = new ItemsCollection(TestUtility.CreateDefaultNSM(), node); itemsCollection.AddSumNode("grand"); Assert.AreEqual(4, itemsCollection.Count); Assert.AreEqual(4, node.ChildNodes.Count); Assert.AreEqual("grand", itemsCollection[3].ItemType); }