@Override
        public void onEvent(ReplicaId replicaId, Object e) {
          if (e instanceof ServerErrorCode) {
            if (e == ServerErrorCode.NoError) {
              successfulResponseCount.incrementAndGet();
            } else {
              invalidResponse.set(true);
            }
          } else {
            failedReplicaIds.add(replicaId);
          }
        }
Response handling related tests for all operation managers.
ambry-router/src/test/java/com/github/ambry/router/NonBlockingRouterTest.java