I've added a few piecemeal tests over the years (all the .t files in the repo), and there's also some tests in my curated repo (http://github.com/akkartik/arc). All those seem ok..
Looks like dfn is a rainbow innovation: http://arclanguage.org/item?id=10539
Update 1 hour later: almost all rainbow tests pass! I had to disable the dfn tests, and the ssyntax tests at the bottom of core-evaluation-test were hanging. Other than that it's all good.
I'll make a pull request later.
I've also added/plagiarized rainbow's tests to the repo: https://github.com/arclanguage/anarki/commit/68be3c0f4d. Joys of the perl artistic license.
There's still a couple of syntax tests that are failing, likely because of test harness issues. And I'd like to unify all the different tests into a single framework. For future work..
Update 43 minutes later: it turns out rainbow's ssyntax precedence rules were different. Perhaps anarki changed at some point. Those tests are now fixed.