travis.debian.net is a hosted service for projects that host their Debian packaging on GitHub to use the Travis CI continuous integration platform to test builds on every update. Amongst many other advantages, this helps catch issues as early as possible and avoids having to run long package builds on one's own computers.
Whilst possible without travis.debian.net , using this service not only avoids unwieldy duplication of configuration, it works around backwards-compatibility issues in supporting tools in older Debian releases.
travis.debian.net additionally supports running autopkgtest tests and disabling network access during builds.