Whichever tools you are used to using on Kali, find OS X versions for them, install and use.
For appsec, Some tools like Burp Suite are platform independent as Burp runs on JAVA which i primarily use and the commercial version is reasonably priced too, OWASP ZAP, w3af, BeEf framework, Nikto etc are all available for download too.
If u are referring to network pentesting, u will find NMAP pre-installed, and u can download Nessus from their website and netcat also comes pre-installed. U will find the move to OS X quite similar as i moved from Backtrack to OS X myself, most tools u are used to should be available on OS X too.
Just install and go with it.
You can look at downloading metasploit here:
If there is something you are used to on other *nix system, and u cant download it for Yosemite, use :
, these will give u all the tools you seek and u can choose which ones to install. I would suggest, discovering your needs and then proceeding to download whatever you need, whenever you need it!
Good luck for your journey!