How do I tell if a plugin uses ARIA correctly?

How do I tell if a plugin uses ARIA correctly?

Hi. I often have to do WCAG accessibility checks as part of my testing job. Part of the specification involves checking that any custom input elements / plugins use ARIA correctly. I can do a check on the source code but quite often the word ARIA doesn't come up. So is there a way to verify that someone's Jquery slider or fancy drop down menu is accessible in this way?