public void Test_AddAll_OnExtendedObservableCollection_Ok() { ICollection <int> collection = new ExtendedObservableCollection <int> { 0 }; collection.AddAll(new List <int> { 1, 2 }); Assert.Equal(3, collection.Count); Assert.Contains(collection, number => number == 0); Assert.Contains(collection, number => number == 1); Assert.Contains(collection, number => number == 2); }