Just install it on a new partition. If you decide not to keep your Yosemite installation, you can simply delete the new partition without affecting your current stable OS X.
Just install it on a new partition. If you decide not to keep your Yosemite installation, you can simply delete the new partition without affecting your current stable OS X.
Before you go installing Yosemite, you need to know that you can't simply erase the partition as usual, because the installer sets up the partition as a Core Logical Group. It isn't hard to covert to journaled. It involves using 2 terminal commands that are very quick to finish. The following is the post you should read.