@Test
  public void testPutPriority() throws Exception {
    testForCall(new ThrowingCallable() {
      @Override
      public void call() throws IOException {
        Put put = new Put(ROW);
        put.addColumn(FAMILY, QUALIFIER, VALUE);
        TABLE.put(put);
      }
    });

  }
Tests that one can implement their own RpcControllerFactory and expect it to successfully pass
custom priority values to the server for all HTable calls.
hbase-server/src/test/java/org/apache/hadoop/hbase/TestCustomPriorityRpcControllerFactory.java