How to copy my Mountain Lion system to another drive? I'm considering upgrading at long last to Mavericks, but need to feel confident that all my apps &amp; workflows will work properly before committing 100%.  I boot off of an external Thunderbolt SSD normally, so that's where my current boot system is (with all my apps installed, etc.).

I have an internal drive with a secondary simple boot partition, also on Mountain Lion.  I basically use it on those occasions I need to boot from a different partition to do disk diagnostics, test things out in a "sandbox" of sorts, etc.

I'm wondering if I can copy my current Mountain Lion system volume - apps and all - to the internal boot partition, and then update THAT drive to Mavericks and run off it for a while until I'm confident that Mavericks is going to work for me.  At that point I would update my SSD and be committed.

Is this viable?  I know that back in the pre-OSX days it was trivial to just copy a system folder and presto - it would boot on a different drive.  But I'm not quite sure this is still the case.

To reiterate, the internal drive I want to copy my system to is already a bootable system partition, so there should be no special blessing or anything required I would think.
Cloned drives are generally not a problem. You don't want to do a simple drag/drop. 
SuperDuper from ShirtPocket will clone your drive and ensure it's bootable. CarbonCopyCloner will do the same. 

There are some more details in How can I get my laptop&#39;s existing system onto a new replacement drive?