@Override
    public long extract(final ConsumerRecord<Object, Object> record, final long partitionTime) {
        return System.currentTimeMillis();
    }
@Test
    public void extractSystemTimestamp() {
        final TimestampExtractor extractor = new WallclockTimestampExtractor();

        final long before = System.currentTimeMillis();
        final long timestamp = extractor.extract(new ConsumerRecord<>("anyTopic", 0, 0, null, null), 42);
        final long after = System.currentTimeMillis();

        assertThat(timestamp, is(new InBetween(before, after)));
    }