public void GetEmpty()
{
var map = new DocumentMap<string>();
map.Add(5, "test");
map.Add(0, "test3");
map.Add(2, "test2");
var relativeRanges = map.GetRelativeRange(new Range(1, 7));
Assert.AreEqual(3, relativeRanges.Count);
Assert.AreEqual("test3", relativeRanges[1].Source);
Assert.AreEqual(new Range(0,0), relativeRanges[1].Range);
}