Various implementations of par but not in C. The par
command formats paragraphs, see man page.
The idea is to rewrite par
in many languages as an continuous exercise to explore the languages and have a useful solution that formats a paragraph in a great way.
The file with tests must be used to validate all implementations. If it's good enough for the original C version then any other implementation must meet that contract. There is no reason for the tests in that file to differ from the upstream.