How can I use jQuery validation with the "chosen" plugin?

jQuery validate ignores the hidden element, and since the Chosen plugin adds visibility:hidden attribute to the select, try:

$.validator.setDefaults({ ignore: ":hidden:not(select)" }) //for all select

OR

$.validator.setDefaults({ ignore: ":hidden:not(.chosen-select)" }) //for all select having class .chosen-select

Add this line just before validate() function. It works fine for me.

jQuery validation isn't going to pick up elements that are hidden, but you can force it to validate individual elements. Bit of a hack, but the following will work:

$('form').on('submit', function(e) {
    if(!$('[name="test2"]').valid()) {
        e.preventDefault();
    }
});  

To select only "chosen" elements you can use $('.chzn-done')