pub fn prepare_test_cluster_env(
cluster: &ClusterConfig,
) -> Result<String, String>Expand description
Prepare the testing-cluster envelope (FLODL_TESTING_CLUSTER_JSON).
Mirrors prepare_cluster_env for the testing path: clones the
cluster, probes device counts LOCALLY (no SSH — tests run
in-process on the local host), populates ranks by sequential
assignment, then serializes for shipping.
Returns the hex-encoded envelope ready to set in the env. Errors
surface from cluster.validate() (structural), the local probe,
or populate_ranks (count/worker mismatch).