Add a FunctionalJavascript test for the jQuery.fn.selectAll functionality

I was able to test this as follows:

1. Install Drupal with the Standard install profile, and enable the Multiselect module
2. Add a field of type List (text) to the Article content type, give it 3 allowed values ("Lorem", "Ipsum", "Dolor"). Set its cardinality to "Unlimited".
3. Manage form display for the Article content type; set the widget for the new List (text) field to "Multiselect"
4. Add an article; fill in Title with a random value, select values "Lorem" and "Dolor" in the new List (text) field.
5. Save the article.
6. Edit the article, and ensure that the values "Lorem" and "Dolor" in the new List (text) field are still selected.

When the jQuery.fn.selectAll functionality was broken, there were no values selected in step 6.

... hopefully this helps whomever ends up writing the test.

Hi @mparker17
I've created the test for it. I have reproduced the same steps as in your comment.
Please check it.

@bobi-mel, looks great! There are a few PHPCS notices; I can fix those before merging. Thank you very much!

@mparker17

I've fixed PHPCS notices

Great, thanks! Merging!

Automatically closed - issue fixed for 2 weeks with no activity.