The ability for gpg-crypt to generate a test tarball is useful, but a step further would be the ability (configure option, defaults to disabled) to simply install the test suite for use on the target. This way there's no need to tarball up the tests, simply install the test cases, data, and test driver.

https://wiki.gnome.org/Initiatives/GnomeGoals/InstalledTests is a good overview of the benefits of installable tests. You can ignore the .test files if you wish.