I recommend using CassandraUnit (https://github.com/jsevellec/cassandra-unit
). It makes using Cassandra in unit tests quite easy.
It allows you to start an embedded Cassandra synchronously with a single simple method call, optionally load your schema and initial data, and you're ready to start testing.
I'm using it in many unit tests (although formally it's not a unit test anymore when relying on a cassandra node). The fantastic performance of Cassandra even allows me to clear all column families and insert the test fixture rows for each individual test case.