public void ItemCollectionItemsSourceTest() { ObservableCollection<string> collection = new ObservableCollection<string>(new[] { "collection1", "collection2", "collection3" }); InnerCollectionView view = new InnerCollectionView(); view.Add("view1"); view.Add("view2"); view.Add("view3"); view.CurrentItemIndex = 1; ItemCollection itemCollection = new ItemCollection(); NotifyCollectionChangedEventArgs lastChangeArgs = null; int currentChangedCount = 0; itemCollection.CollectionChanged += (sender, e) => lastChangeArgs = e; itemCollection.CurrentChanged += (sender, e) => currentChangedCount++; itemCollection.SetItemsSource(collection); Assert.AreEqual(-1, itemCollection.CurrentItemIndex); Assert.AreEqual(1, currentChangedCount); collection.Add("collection4"); Assert.AreEqual(NotifyCollectionChangedAction.Add, lastChangeArgs.Action); CollectionAssert.AreEqual(new[] { "collection4" }, lastChangeArgs.NewItems.Cast<string>().ToArray()); Assert.AreEqual(-1, itemCollection.CurrentItemIndex); Assert.AreEqual(1, currentChangedCount); itemCollection.CurrentItemIndex = 0; Assert.AreEqual(0, itemCollection.CurrentItemIndex); Assert.AreEqual(2, currentChangedCount); itemCollection.SetItemsSource(view); Assert.AreEqual(NotifyCollectionChangedAction.Reset, lastChangeArgs.Action); CollectionAssert.AreEqual(new[] { "collection1", "collection2", "collection3", "collection4" }, lastChangeArgs.OldItems.Cast<string>().ToArray()); CollectionAssert.AreEqual(new[] { "view1", "view2", "view3" }, lastChangeArgs.NewItems.Cast<string>().ToArray()); Assert.AreEqual(1, itemCollection.CurrentItemIndex); Assert.AreEqual(3, currentChangedCount); itemCollection.SetItemsSource(collection); lastChangeArgs = null; view.Add("view4"); Assert.IsNull(lastChangeArgs); }