Github user aljoscha commented on the issue: https://github.com/apache/flink/pull/5652 @StephanEwen I think that's what the interface already does. For example, `MiniClusterClient.submitJob()` does a `miniCluster.runDetached(jobGraph)`, and `MiniClusterClient.cancel()` does `miniCluster.cancelJob(jobId)`. The problem is that the legacy cluster does not have methods for those things, namely "cancel", "get job status", "get accumulators", and "savepoint". All existing ITCases use custom Akka communication with the testing cluster. We can either add methods for all that to the legacy mini cluster (that would probably also use Akka) or use the `StandaloneClusterClient`, which also uses Akka. But for those Akka messages to work we can't run it in single-actor-system mode. WDYT?