Hi Brett, and great you are interested in testing
because there is lots to test!
If you dont find a ticket you can simply go to
and browse through classes that have low coverage, you will even find some with no test at all but still quite a lot of lines of code.
You can also generate coverage locally either in your IDE or with
mvn clean package && mvn jacoco:report the coverage reports will then be in the
target/site sub folders.
I dont think we necessarily need a ticket if you just add tests without changing any production code.
We have some documentation about how we test here https://wiki.openmrs.org/display/docs/Testing, but I think the docs need some updates, so if you have questions just ask us