public void TestRemoveAndAdd_RemovedAndAdded()
        {
            _set.CollectionChanged += (sender, args) =>
            {
                CollectionAssert.AreEquivalent(new[] { "item 3" }, args.RemovedItems);
                CollectionAssert.AreEquivalent(new[] { "item 4" }, args.AddedItems);
            };

            _set.RemoveAndAdd("item 3", "item 4");

            CollectionAssert.AreEquivalent(new[] { "item 1", "item 2", "item 4" }, _set);
            ExpectChangeCalls(1, 0);
        }