Undo() public method

Performs an undo.
public Undo ( ) : void
return void
        public void when_attempting_to_version_a_property_bag()
        {
            var originalAddress = "12345 Fake Street";
            var subscriber = new SimpleMementoingClass()
                                 {
                                     Domainees = new List<DomainPropertyBag>()
                                                     {
                                                         new DomainPropertyBag(),
                                                         new DomainPropertyBag()
                                                     },
                                     ChiefDomainee = new DomainPropertyBag(),
                                     Address = originalAddress,
                                     FirstName = "If only Customer Objects",
                                     LastName = "were ever this simple"
                                 };

            var mementor = new Mementor();

            var newAddress = "Changed Address!";
            mementor.PropertyChange(subscriber, () => subscriber.Address);
            //ohhh typing is a little weak here.
            subscriber.Address = newAddress; //ahh, note the order matters of course.

            subscriber.Address.Should().Be(newAddress);

            mementor.Undo();
            //and I cant undo specific changes, just the last one.

            subscriber.Address.Should().Be(originalAddress);
            //still, very cool.
                //In terms of a deployed program, this is tough to implement.
                //I like the pub-sub design of it, code is superbly clean.
        }
        public void when_attempting_to_restore_an_externally_tracked_list()
        {
            var mementor = new Mementor(isEnabled: true);

            var collection = new List<string>();
            var item = "hey!";
            mementor.ElementAdd(collection, item);//this is an extension method? Oh I see, he didnt want to put custom-list logic on Mementor. Nice.
            //it also doesnt actually add the element to the list:
            collection.Add(item);
            collection.Should().HaveCount(1);

            mementor.Undo();
            //hmm, so it expects the caller to do the Add but it will handle the remove?

            collection.Should().BeEmpty();
        }