atf-c-api(3) on FreeBSD
The text 79cddd31bfd0, as FreeBSD 13.3-RELEASE, FreeBSD 13.2-RELEASE, FreeBSD 13.1-RELEASE, FreeBSD 13.0-RELEASE, FreeBSD 12.4-RELEASE, FreeBSD 12.3-RELEASE, FreeBSD 12.2-RELEASE, FreeBSD 12.1-RELEASE, FreeBSD 12.0-RELEASE, FreeBSD 11.4-RELEASE, FreeBSD 11.3-RELEASE, FreeBSD 11.2-RELEASE shipped it.
C API to write ATF-based test programs