We've released DrFed 0.1.0, the first version of the ActivityPub development and debugging tool I'm building with the team.
It's still an MVP: you can create test instances and actors, and inspect incoming activities. I wouldn't call it a particularly useful debugger yet. We wanted to share what we've built so far and let people know that development is continuing.
We're working toward a tool that helps when your ActivityPub app won't federate with another server. Thanks to my teammates for getting us to this first release. I hope you'll follow along.