EmptyMap extends EvalFunc<Map<String, String>> { @Override public Map<String, String> exec(Tuple tuple) throws IOException { return Collections.emptyMap(); }  @Override Map<String, String> exec(Tuple tuple); @Override Schema outputSchema(Schema input);  }
@Test public void testExec() throws Exception { Map<String, String> result = udf.exec(null); assertTrue(result.isEmpty()); }