With the help of the community I’ve built an embedded cassandra service ideal for unit testing and perhaps other uses. I’ve also built a cleanup utility that helps wipe out all data before the service starts running so the combination of both provides isolation etc. Now each test process runs an in-process, embedded instance of cassandra.
While I do agree with the main goal behind this initiative (i.e. testability), I do think that a stub solution (take for example RockingChair a Ruby stub library for CouchDB) would be a much better fit and would perform a lot better. As the original post mentions, the embedded Cassandra service requires each test to be run in a separate JVM and as you can imagine that will be far from being quick.