On GNU/Linux, these utilities are a part of the coreutils, the test suite can be found in the source repository under tests.
Note: Linux is just the kernel, the rest of the system is developed by different entities, such as GNU.
GNU is an operating system that is free software...consists of GNU packages (programs specifically released by the GNU Project) as well as free software released by third parties.
On BSD, the whole operating system is developed together in one repository.
For OpenBSD, there do not appear to be any tests for these utilities in their source repository.
