public void replacing_an_item_updates_the_minimum_if_it_has_changed()
{
var model = new PostedTimeCollectionModel();
var observer = model.CreateObserver();
var replacement = PT(20, PostedTimeType.Normal, 1);
model.Add(PT(30, PostedTimeType.Normal, 1));
observer.ClearChanges();
model.ReplaceCurrent(replacement);
Assert.Equal(replacement, model.Minimum);
Assert.True(observer.HasChanged(x => x.Minimum));
model.Add(PT(10, PostedTimeType.Normal, 1));
observer.ClearChanges();
replacement = PT(5, PostedTimeType.Normal, 1);
model.ReplaceCurrent(replacement);
Assert.Equal(replacement, model.Minimum);
Assert.True(observer.HasChanged(x => x.Minimum));
}