Here is a list of some tickets that can give you a good starting point for hacking on OONI.
Some are easier than others to solve.
# Easy tickets
ooni test decks specifying logfile path but it is not used: https://github.com/TheTorProject/ooni-probe/issues/123
Verify the version of config files: https://github.com/TheTorProject/ooni-probe/issues/190
ooni crashes if no collector option is used with several decks: https://github.com/TheTorProject/ooni-probe/issues/274
# Harder tickets
Add support for storing the order in which HTTP headers are received: https://github.com/TheTorProject/ooni-probe/issues/254
Add support for having multiple test classes inside of a nettest file: https://github.com/TheTorProject/ooni-probe/issues/289
Recursion limit problem in TaskManager: https://github.com/TheTorProject/ooni-probe/issues/296
Detect when a probe is using the wrong test helpers: https://github.com/TheTorProject/ooni-probe/issues/158
If you have any questions on these tickets you should either comment on the issue tracker or reply to this email thread.
Happy hacking!
~ Art.