An autopkgtest is also the name for such a test suite.
It can be helpful to run tests locally to make sure everything is working. Here are the steps to do that.
First you want to get a Debian image. autopkgtest provides a utility to easily build an image.
- sudo autopkgtest-build-qemu unstable autopkgtest-unstable.img
This creates an image with debian unstable on it.
Now you can use this image to test your source package (gdk-pixbuf):
- autopkgtest gdk-pixbuf -- qemu autopkgtest-unstable.img
This will run the tests located in debian/tests.