@Test
public void testFlattenPrefix()
    throws JsonSyntaxException, UnsupportedEncodingException, IOException {

  JsonParser parser = new JsonParser();
  JsonElement input = parser.parse(getResourceString("flatten_prefixed_input.json"));
  String expectedOutput = getResourceString("flatten_prefixed_output.json");
  DummpyEvent devent = new DummpyEvent();
  devent.payload = input.getAsJsonObject();
  GelfOperation op = new GelfOperation(new ArrayList<>());
  InternalEvent ievent = new InternalEvent("", null, 0);
  ievent.setEventObj(devent);
  op.perform(ievent);
  assertEquals(parser.parse(expectedOutput), devent.payload);
}