Selector trouble

Selector trouble

Hopefully this is an easy one, but I'm having trouble getting a selector working.   Probably best just to give you some example code:

HTML
  1. <input type='button' class='test' value='Button Name'>
  2. <div>
  3. <a href='' class='buttonLink' />Click me</a>
  4. </div>
Jquery

  1. $(.buttonLink).click(function() { $(this).closest(':button.test').addClass('testclass'); });
Form that code I would expect the class of 'testclass' to be applied to the button after the link is clicked, but It doesn't seem to work. 

This is a somewhat contrived example.  In my real application I have a form with several collapsable/expandable sections.  If the fields in those form sections have values when the page loads, the section needs to be expanded, and the expand/collapse button needs to have a class of 'expaned' applied to it, if not it needs to be hidden.  I can check the form fields and show the div if needed without any problem, but I can't seem to figure out how to work out the selector so I can add the class to the button.