And ignore the orthodox Debianeers who say "nobody should be using testing".

Testing is not really a rolling release and is not guaranteed to get security updates in a timely manner so it's certainly not for everyone.

Testing is a rolling release for most of the time. As well as Sid is:

Sid [rolling] -> Testing [rolling] -> Stable [point release]

This is only true until testing gets frozen. After a freeze gets lifted again, many transitions might occur. I use it myself but it's wrong to call it a rolling release that everyone should use.

testing is absolutely not a rolling release. Sure it gets new packages faster than stable which can appear to be the same as a rolling release it gets frozen before a stable release and suddenly it's not a rolling release.

So to describe it precisly: Debian Testing is a rolling release for majority of time. When the Stable is going to be released, Testing gets frozen for a while. But then it becomes the rolling release again. Debian stable gets released once in ~2 years. So once in ~2 years Debian testing is not a rolling release.