I started working on some unit testing around when Dash 2.6 released; however, I ran into some import errors. I believe these have since been fixed, so its just a matter of time before someone (myself included) opens a pull request into this repo to address them.
As for testing beyond the unit variety, I don’t have the most experience with integrating these in the Dash ecosystem. Ideally tests of all varieties are kept in the /tests directory (this is in the repo already). Again, I am open to any and all Pull Requests to further improve this repo!