Which Macs, both desktop and portable, support HDCP on their native displays? The web is awash with information on connected displays, and which support it, don't support it, and stories of people who weren't warned that theirs don't support it, paid $15 for a movie, and are now screwed.
But for internal displays, I can find nothing. Apple's own Technical Specifications do not list HDCP support. Everymac.com has nothing. I was once able to play an HD iTunes movie on my Late 2008 MacBook Pro, but had to take a leap of faith that it supported HDCP. A StackOverflow answer indicates even a motivated developer couldn't make an app that determines whether a given Mac has HDCP support for its built-in display.
It seems the only way - not exaggerating here - is to buy some protected content from iTunes and hope it works.