How to switch to testing branch?

[Vojtěch šmiro <vsmiro@seznam.cz>]

Hello,

I have Debian 10 Buster on my desktop PC. How can I switch to testing 
branch? I don't like reinstalling systems when Pulse-eye will be 
downloadable and many people recommend testing which is better to have 
and have the newest system. I know, it might be a risk, but I have 
backup of my data and system if something go wrong.

Thanks a lot.

Best regards

Vojta.