During a release we track the status of testing images as we go. This is coordinated in IRC on irc.debian.org #debian-cd.

Link to the test pages should be added here:

Bullseye (Debian 11)

Buster (Debian 10)

Stretch (Debian 9)

Jessie (Debian 8)

Wheezy (Debian 7)

Squeeze (Debian 6)