@Override
  public List<NetworkReceive> completedReceives() {
    if (state == MockSelectorState.IdlePoll) {
      return new ArrayList<>();
    }
    List<NetworkReceive> toReturn = receives;
    receives = new ArrayList<>();
    return toReturn;
  }
Returns a list of {@link NetworkReceive} constructed in the last poll to simulate a response for every send.
@return a list of {@line NetworkReceive} for every initiated send.
ambry-network/src/test/java/com/github/ambry/network/SocketNetworkClientTest.java