to know what you have on a particular repo :

$ pacman -Sl obarun-testing

to know the dependancies of every package on the repo installed on your system

$ for i in $(pacman -Sl obarun-testing); do pactree -r $i 2>/dev/null; done

So, safe and testing are not compatible :). If you want a stable system, it's never a good idea to enable a testing repo whatever the distro you use. You should know what you exactly do when you install a package from a testing repo.
I'm not sure to understand exactly what you mean by "dependancies trouble"