location of atf-scripts on github

[Fred Schlechter]

My question is on the location, in the FreeBSD source-tree on github, of the atf-scripts.

For example, to test the basename(1) utility there is an atf-script named basename_test
in /usr/tests/usr.bin/basename/ on my FreeBSD workstation. But, I can't find the file
basename_test anywhere in the FreeBSD source tree on github.

But, in the NetBSD source-tree on github there is a file named t_basename.sh in
netbsd-src/tests/usr.bin/basename/. The basename_test file, which FreeBSD uses, seems
to be based on the NetBSD file.

Please explain, where are the FreeBSD-specfic atf-scripts on github or in another repo?

Thanks,
FJS