private List<MockDataNodeId> buildDataNodeList(List<ReplicaSpec> replicaSpecs) {
    List<MockDataNodeId> dataNodes = new ArrayList<MockDataNodeId>();
    for(ReplicaSpec replicaSpec : replicaSpecs) {
      dataNodes.add(replicaSpec.getDataNode());
    }
    return dataNodes;
  }
Generates a list of {@link MockDataNodeId} based on the given {@link ReplicaSpec}.
@param replicaSpecs
@return a list of {@link MockDataNodeId}.
ambry-router/src/test/java/com/github/ambry/router/ParanoidDurabilityOperationTrackerTest.java