I've put together some tests as a skeletal place to start with Solr tests. I'll add a zip file in a few minutes. They do a really simple ping, one indexes a few documents and searches, and one verifies that we can get to the filterCache statistics.
This is very preliminary. The zipped up tests run against a locally-built Solr, NOT the one that will be packaged with BigTop. And I haven't a clue how to integrate them with the actual package, (any hints welcome). This is meant as a starting place.
Of course to be done for real we'll need to create an actual patch, but I'm guessing we'll need to sequence that after the base Solr gets into the packaging, the zip file is meant as a record to build upon when we actually get this all together.