AssertJ is a set of projects aiming at easing test assertions in Java.
One module I started is AssertJ-Neo4j, which provides assertions tailored for Neo4j Java APIs.
If you are interested in contributing to the Neo4j ecosystem, AssertJ-Neo4j is an ideal project to get started. The learning curve is fairly small and there is a number of small, good first issues to tackle.
The codebase is very consistent and looking at existing assertions will help you figure out how to structure the new ones you are adding. You can also improve the documentation and add new examples in https://github.com/joel-costigliola/assertj-examples/.
Have a look at the repository today and join the growing community of contributors!