This is a proposal for GSoC2013:
Apache Oak is creating the next version of Apache Jackrabbit. It will be highly scalable, capable of web scale deployment. Apache Sling will use Apache Oak as its central repository, however, this work is very new. The taks of making Sling available on Oak is almost complete, however the task of integration testing has not been started.
Within Sling there are a large number of integration tests that verify the operation of Sling. This GSoC project is to work with Apache Sling ontop of Apache Oak and fix the integration tests providing patches to Apache Sling and potentially to Apache Oak.
Who ever gets accepted to work on this project will learn an immense amount about the internals of both Sling and Oak and, assuming there are bugs will provide an extremely valuable contribution Sling and potentially Oak.
There is some risk in applying for this project, as Sling may work perfectly ontop of Oak first time, although I think this is unlikely.
Advanced Java skills are required, knowledge of Integration testing, JUnit and OSGi are also required.
Some knowledge of JCR, Jackrabbit, Sling and Oak will be advantageous.
The following pages give more information about GSoC @apache: