AVR simulator for mac?

As Atmel Studio is unfortunately unavailable for mac, has anyone had any experience of AVR simulators for OS X?

There seems to be a few products such as MacSim, however, it only supports a limited number of chips.

I'm working with embedXcode to program my Arduino Mirco (ATmega32U4), however, there is no debugging and I would really like to have a software simulator where I can inspect registers easily.