Here is an idea. If the development environment does not have any Unit tests, start him/her off to write Unit Tests. This will help improve the stability of the system, get additional documentation, have some of their real-world work to evaluate, and they can learn about the system in pieces...
If the system already has unit tests, check what the existing code coverage is and provide a resonable new target % to achieve code coverage upon with new Unit Tests. This is a bit more tricky and would require some hand holding.
