There are several extensions and related tools that do much of that. You should look at nbgrader and exercise and exercise2 for showing solutions, see here.
Also check out Teaching remotely with Jupyter: tips, resources, and best-practices .
For testing you may also be interested in: nbdev, testipynb, or “I’ve hacked our open-source repository of California coronavirus data to demonstrate how you can use nbclient and @github actions to test and verify @ProjectJupyter notebooks with each commit. GitHub - datadesk/california-coronavirus-data: The Los Angeles Times' open-source archive of California coronavirus data”, posted here