Very Selective upgrade

[Tom Allison]

Can someone give me an example of how I would upgrade a specific 
package from 'testing' without affecting any of the apt-get libraries?
If I change the sources.list to include 'testing' then I get all 
kinds of files selected for upgrade.  I really don't want to move 
anything out of 'stable' right now as I've tried repeated upgrades 
and they all result in a horrific system failure.
I've got 'stable' installed, but I want to include the 'testing' 
version of openSSH...