A tutorial on how to implement functional testing in your packages using the DEP-8 standard (a.k.a autopkgtest) in a way that the Debian CI will automatically run it for you. I will explain the foundations of the DEP-8 spec, how to run tests on your own development box, commons tips and tricks for writing tests (e.g. how to run the upstream test suite), and present several examples from packages in the archive.