public void DetachStopsListeningForChanges()
        {
            var region = new MockPresentationRegion();
            var behavior = new RegionActiveAwareBehavior { Region = region };
            var collection = region.MockActiveViews.Items;
            behavior.Attach();
            behavior.Detach();
            ActiveAwareFrameworkElement activeAwareObject = new ActiveAwareFrameworkElement();

            collection.Add(activeAwareObject);

            Assert.IsFalse(activeAwareObject.IsActive);
        }