How to debug minikube errors?
Your pod is in CrashLoopBackoff state. This means that the container inside your pod is terminating its execution, kubernetes is trying to run it again, but it terminates again, giving you a Crash Loop.
I suggest you to take a look at the container's output by running:
kubectl -n test logs -f cassandra-6b5f5c46cf-zpwlxThat should be cassandra's output and should explain the reason cassandra is not running.