@Test
public void extractNoValues(){

    MRecord record2 = UntypedValues.builder().source("source").timestamp(123L).values(Collections.emptyMap()).build();
    EvaluationContext<MRecord> context2 = new SimpleEvaluationContext<>(record2);
    Map<String, Value> extract = extractor.extract(context2);
    assertEquals(0, extract.size());
}