Who shall watch the watchers?
I agree that a test of ethics, intelligence, character and personality, plus a psychological examination,should be mandatory for not only politicians but also any senior people (board members, directors and other senior executives) in public service AND private companies.
But anyone who didn't pass, and everyone on the lunatic fringe, would argue that no one is qualified to administer that test.
I reckon an independent body could do it, led by someone prominent and above reproach (Australian of the year for services to charity, for example), with evidence based support from professorial subject matter experts from leading universities, and highly vetted staff.