Add more dag related tests for aria-labelledby associations

[zepumph]

We are testing dag pretty well one just 1 case (when you are labelledby yourself).

[zepumph]

@jessegreenberg could you help me out with this one? Or maybe could we do it together?

[zepumph]

I thought about one more test that would be nice here, relating to having accessible content or not.

    var m = new Node();
    var n = new Node( {tagName: 'div' });
    m[ addAssociationFunction ]( {
      otherNode: n,
      thisElementName: AccessiblePeer.PRIMARY_SIBLING,
      otherElementName: AccessiblePeer.LABEL_SIBLING
    } );
    
    m.tagName = 'div';
    /* test */

    var m = new Node();
    var n = new Node();
    m[ addAssociationFunction ]( {
      otherNode: n,
      thisElementName: AccessiblePeer.PRIMARY_SIBLING,
      otherElementName: AccessiblePeer.LABEL_SIBLING
    } );

    m.tagName = 'div';
    n.tagName = 'div';
    /* test */

[jessegreenberg]

Good idea @zepumph. In a dev meeting a while ago, we added more tests to verify behavior after other changes to the scene graph such as adding/removing children, reordering children, and more than one association. I also took a look at the way describedby is being tested in the same way, it looks very nice. Removing my assignment for now, but feel free to reassign if you wish.

[zepumph]

• Another test that would be good would be to add the same object twice. I think that we should detect this and throw an error. What do you think @jessegreenberg?