public void GivenMultipleElementAreInTheModelWhenPreviousSiblingIsCalledOnOtherElementThanTheFirstThenPreviousElementIsReturned()
{
DsmElementModel model = new DsmElementModel();
Assert.AreEqual(1, model.GetElementCount());
IDsmElement a = model.AddElement("a", "", null);
Assert.AreEqual(1, a.Id);
IDsmElement a1 = model.AddElement("a1", "eta", a.Id);
Assert.AreEqual(2, a1.Id);
IDsmElement a2 = model.AddElement("a2", "eta", a.Id);
Assert.AreEqual(3, a2.Id);
IDsmElement a3 = model.AddElement("a3", "eta", a.Id);
Assert.AreEqual(4, a3.Id);
Assert.AreEqual(null, model.PreviousSibling(a1));
Assert.AreEqual(a1, model.PreviousSibling(a2));
Assert.AreEqual(a2, model.PreviousSibling(a3));
}
