@Parameters(name = "{index}: rpcServerImpl={0}, rpcClientImpl={1}")
  public static List<Object[]> params() {
    List<Object[]> params = new ArrayList<>();
    List<Class<? extends RpcServer>> rpcServerImpls =
      Arrays.asList(NettyRpcServer.class, SimpleRpcServer.class);
    List<Class<? extends RpcClient>> rpcClientImpls =
      Arrays.asList(NettyRpcClient.class, BlockingRpcClient.class);
    for (Class<? extends RpcServer> rpcServerImpl : rpcServerImpls) {
      for (Class<? extends RpcClient> rpcClientImpl : rpcClientImpls) {
        params.add(new Object[] { rpcServerImpl, rpcClientImpl });
      }
    }
    return params;
  }
Tests for HBASE-28321, where we have multiple server principals candidates for a rpc service.
<p>
Put here just because we need to visit some package private classes under this package.
hbase-server/src/test/java/org/apache/hadoop/hbase/ipc/TestMultipleServerPrincipalsIPC.java