Quality Assurance

Debian has several technical means to assure a constant high level of quality:

There are periodical tests to rebuild all software targeting a future release. This verifies compilation against recent build tools and might uncover technical problems in software. This is an additional check to the build daemons mentioned below.
Automated upgrade checks
Before a new version of Debian is released, automated tests are done, where every single package will be automatically installed into a clean stable system of the last published Debian release and then the system will be upgraded to the future stable release. This makes sure that new Debian releases can be rolled out smoothly in release critical applications.
Package Installation and De-installation
The tool piuparts tests that .deb packages (as used by Debian) handle installation, upgrading, and removal correctly. It does this by creating a minimal Debian installation in a chroot, and installing, upgrading, and removing packages in that environment, and comparing the state of the directory tree before and after.

Andreas Tille 2010-12-10