Add two failing tests for fixing

Author: shana

src/TrackingCollectionTests/ListenerCollectionTests.cs

@@ -16,6 +16,17 @@ public void Setup()
     }
 #endif
 
+    [Test]
+    public void StickyItemShouldNotBePresentInitiallyWhereNoSelectionHasHappened()
+    {
+        var source = CreateSource();
+        var stickie = new Thing();
+        var selection = Observable.Empty<Thing>();
+        var target = source.CreateListenerCollection(stickie, selection);
+
+        CollectionAssert.AreEqual(source, target);
+    }
+
     [Test]
     public void StickyItemShouldNotBePresentAfterCreationWhenSelectionNull()
     {
@@ -109,6 +120,20 @@ public void StickyItemShouldBeRemovedWhenSelectionChangesToStickyItem()
         CollectionAssert.AreEqual(source, target);
     }
 
+    [Test]
+    public void ResetingTrackingCollectionWorks()
+    {
+        var source = CreateSource();
+        var stickie = new Thing();
+        var selection = new ReplaySubject<Thing>();
+        var target = source.CreateListenerCollection(stickie, selection);
+        selection.OnNext(stickie);
+        selection.OnNext(null);
+        CollectionAssert.AreEqual(source, target);
+        source.Filter = (a,b,c) => true;
+        CollectionAssert.AreEqual(source, target);
+    }
+
     TrackingCollection<Thing> CreateSource()
     {
         var result = new TrackingCollection<Thing>(Observable.Empty<Thing>());