public void ReplaceAllShouldClearAndAddRange() { // arrange var oldItems = new List<object>() { new object(), new object(), new object() }; var newItems = new List<object>() { new object(), new object(), new object() }; var target = new Collection<object>(); target.AddRange( oldItems ); // act target.ReplaceAll( newItems ); // assert Assert.Equal( newItems.Count, target.Count ); Assert.True( target.SequenceEqual( newItems ) ); }