public void ObservableWhere_AddRemoveTest()
{
var source = new ObservableCollection<int>(Enumerable.Range(0, 10));
var target = source.ObservableWhere(s => (s & 1) != 0);
NotifyCollectionChangedEventArgs lastEventArgs = null;
NotifyCollectionChangedEventHandler callback = (_, e) => lastEventArgs = e;
target.CollectionChanged += callback;
source.Remove(2);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 3, 5, 7, 9 }));
Assert.IsNull(lastEventArgs);
source.Remove(3);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 5, 7, 9 }));
Assert.AreEqual(NotifyCollectionChangedAction.Remove, lastEventArgs.Action);
Assert.AreEqual(3, lastEventArgs.OldItems[0]);
lastEventArgs = null;
source.Remove(4);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 5, 7, 9 }));
Assert.IsNull(lastEventArgs);
source.Remove(5);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 7, 9 }));
Assert.AreEqual(NotifyCollectionChangedAction.Remove, lastEventArgs.Action);
Assert.AreEqual(5, lastEventArgs.OldItems[0]);
lastEventArgs = null;
source.Add(4);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 7, 9 }));
Assert.IsNull(lastEventArgs);
source.Add(5);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 7, 9, 5 }));
Assert.AreEqual(NotifyCollectionChangedAction.Add, lastEventArgs.Action);
Assert.AreEqual(5, lastEventArgs.NewItems[0]);
lastEventArgs = null;
source.Insert(2, 5);
Assert.IsTrue(target.SequenceEqual(new[] { 1, 7, 9, 5, 5 }));
Assert.AreEqual(NotifyCollectionChangedAction.Add, lastEventArgs.Action);
Assert.AreEqual(5, lastEventArgs.NewItems[0]);
}
