@duncanbeevers I would not create another variable, ie `shouldUpdateValue`, just to use it once in an `if` statement 1 line below. If this seems a bit magic, it's better to add a comment, rather than trying to clarify things with variable names.

About the `undefined`, I think the tests pass even if you use `null`, but I am not sure :-). If yes and the `undefined` has a special meaning, you should provide another test for this.