Debian testing is the current development cycle of Debian.
A package is installed into the testing dist from DebianUnstable automatically when a list of requirements is fulfilled:
- The package is at least 10 days old.
- The package has been built for all the architectures which the present version in testing was built for.
- Installing the package into testing will not make the distribution more uninstallable.
- The package does not introduce new release critical bugs.
These requirements should assure that testing is in a pretty workable state but still developing. Especially when packages get restructured, packages that are not quite releasable get into testing, so not all the fun of using a developmental version is removed.
An example of testing's unstableness is the upgrade from perl-5.6.0 to perl-5.6.1 which made perl unable to find its modules if they were from a package built with perl-5.6.0. Setting the environment variable ["PERL5LIB"] to /usr/lib/perl/5.6.0 solved the problem.
Testing has the worst security update speed compared to stable and unstable. Don't prefer testing if security is a concern. (is this still valid after 2005-06-06?)
DebianEtch is the current testing distro. If you were tracking DebianTesting but really meant to be tracking DebianSarge, update your /etc/apt/sources.list replacing 'testing' with 'sarge'. The 'sarge' alias would have tracked 'sarge' through it's transition into 'stable'. You can do the same for DebianEtch.
You can see what distribution an alias is tracking by looking at the Release file; e.g.:
If you wonder why a package (or a particular version thereof) is not yet in testing, see http://bjorn.haxx.se/debian.