The post mentions the existence of an extensive test suite, which you can peruse for yourself if you're so inclined: https://github.com/bitplane/rars/tree/master/crates/rars-for...

I don't know how all these test cases were generated, but at least some of them seem to have been copied (with attribution) from the test suites of earlier FOSS RAR implementations.

The ideal would be to test it against a representative corpus of real-world legacy RAR files, but I'm not sure where you'd find one.