Trying to test my object's ability to save. It has some dependencies on a parent, though. Which test suite should be responsible?

Question

I have an object of type PlaylistItem. In the 'real application', a PlaylistItem will always be added to a Playlist before saving.

However, I am trying to use Jasmine to test my PlaylistItem's save functionality. My first thought was to create a PlaylistItem spec and, inside of that spec, test the PlaylistItem's saving functionality.

Here is my PlaylistItem spec:

define(['playlistItem'], function(PlaylistItem) {
    describe('The PlaylistItem', function() {
        it("instantiates without paramaters", function() {
            var playlistItem = new PlaylistItem();
            expect(playlistItem).not.toEqual(null);
            expect(playlistItem.isNew()).toEqual(true);
            expect(playlistItem.get('id') === null);
            expect(playlistItem.get('playlistId') === null);
            expect(playlistItem.get('videoId') === '');
            expect(playlistItem.get('title') === '');
            expect(playlistItem.get('selected') === false);
            expect(playlistItem.get('relatedVideos') === []);
        });

        it("instantiates with paramaters", function() {
            var title = 'Test Title';
            var playlistItem = new PlaylistItem({
                title: title
            });
            expect(playlistItem).not.toEqual(null);
            expect(playlistItem.isNew()).toEqual(true);
            expect(playlistItem.get('title')).toEqual(title);
        });

        //  TODO: Should playlistItem be responsible for testing is savability, or the playlist itself?
        //  I need a playlist ID to be able to test this successfully, so hard to say
        it("saves", function() {
            var playlistItem = null;
            var title = 'Test Title';
            var videoId = 'C8aBuRCcfSY';

            runs(function() {
                playlistItem = new PlaylistItem({
                    title: title,
                    videoId: videoId
                });

                playlistItem.save();
            });

            waitsFor(function() {
                return playlistItem !== null && !playlistItem.isNew();
            });

            runs(function() {
                expect(playlistItem.get('videoId')).toEqual(videoId);
                expect(playlistItem.get('title')).toEqual(title);
            });
        });
    });
});

and here is the accompanying PlaylistItem:

//PlaylistItems have a one-to-one relationship with a Video object via the videoId property.
define(['programState'], function(programState) {
    'use strict';
    var PlaylistItem = Backbone.Model.extend({
        defaults: function() {
            return {
                //PK is a composite key of playlistId and position so that server and client can both derive PK without waiting on each other.
                playlistId: null,
                position: -1,
                videoId: '',
                title: '',
                selected: false,
                relatedVideos: [] //Not stoked about having these here, but doing it for convenience for now.
            };
        },
        urlRoot: programState.getBaseUrl() + 'PlaylistItem/'
    });

    //Public exposure of a constructor for building new PlaylistItem objects.
    return function (config) {
        var playlistItem = new PlaylistItem(config);
        return playlistItem;
    };
});

My current save test fails because the PlaylistItem's position is -1 and its playlistId is null. Both of these fields are required.

So, my question is: Should PlaylistItem spec couple to Playlist in order to test PlaylistItem 'save,' or does this need indicate that the Playlist spec should test PlaylistItem 'save' ? The latter seems counter-intuitive, but the former seems like a code smell.

Advice appreciated, thanks.