Tests for Zipper are far from sufficient

Reference: https://exercism.io/mentor/solutions/962ebabf19e848e5bceed0533f1898ad#discussion-post-605355

We should add a test similar to:

test('traversal returns a new Zipper object', () => {
    expect(zipper.value()).toEqual(1);
    let left = zipper.left();
    expect(zipper.value()).toEqual(1);
    expect(left.value()).toEqual(2);
  })

This seems to be a pretty key thing to not test for.

I don’t actually think the students exact implementation is super critical here. What they did was implement a single object with a “cursor” that kept track of where it was in the tree and acted accordingly. So that calling left or right would merely update the cursor position…

Which 100% works since the current tests never require that a new object be generated.

[joshgoebel]

Oh I forgot we had those sample solutions. 😃

Oh, setting is suppose to make new zippers too? Yeah, even my own solution is doing this way wrong… starting to sound like a uber functional exercise. 😃

They all have their own “pointers”, but they all point to the same nodes. That is correct.

When I hear pointer I think of the object property, not the object itself… Ie Zipper#focusNode is the pointer, since it’s literally pointing at the node… but I see how you’d come to think of the higher level object as doing the same thing, despite it really just holding the pointer.

[SleeplessByte]

It doesn’t. But for now this is all we can do, because I want to keep following the problem-specifications readme format. I don’t want to have to keep track “which exercises have a special readme” as often we mass re-generate all the readme’s.

In v3 this is fixed! So it’s only a concern for now anyway. 😃