### Question:
JsonAndKeyCombiner implements Func1<JsonElement, KeyAndJson> { @Override public KeyAndJson call(JsonElement jsonElement) { return new KeyAndJson(mKey, jsonElement); } JsonAndKeyCombiner(String key); @Override KeyAndJson call(JsonElement jsonElement);  }### Answer:
@Test public void testCombiner() { KeyAndJson result = mCombiner.call(mStats); assertNotNull(result); assertEquals(result.key, "2015necmp"); assertNotNull(result.json); assertTrue(result.json.isJsonObject()); assertEquals(mStats, result.json); }