@Test
  public void testAppendMetaTable() {
    conn.getTable(TableName.META_TABLE_NAME).append(new Append(Bytes.toBytes(0))
      .addColumn(Bytes.toBytes("cf"), Bytes.toBytes("cq"), Bytes.toBytes("v"))).join();
    verify(stub, times(1)).mutate(assertPriority(SYSTEMTABLE_QOS), any(MutateRequest.class), any());
  }
Confirm that we will set the priority in {@link HBaseRpcController} for several table operations.
hbase-client/src/test/java/org/apache/hadoop/hbase/client/TestAsyncTableRpcPriority.java