[Qerub]

Debian testing doesn't get timely security updates so it's inappropriate to use on production servers.

Source: https://www.debian.org/security/faq#testing

[bayindirh]

I know. However, back then testing also was getting security fixes with 24h deadline but, since Debian got much bigger, it became unfeasible and abandoned, no biggie.

I always deploy current stable to any production server and I keep my desktop systems in rolling testing.