public void adding_an_item_updates_the_range()
{
var model = new PostedTimeCollectionModel();
var observer = model.CreateObserver();
model.Add(PT(1d, PostedTimeType.Normal, 1));
Assert.Equal(TS(0d), model.Range);
model.Add(PT(10d, PostedTimeType.Normal, 1));
Assert.Equal(TS(9d), model.Range);
Assert.Equal(2, observer.GetChangeCount(x => x.Range));
}