drain producer records in kafka streams topology test driver

gistfile1.txt

    private <K, V> List<ProducerRecord<K, V>> drainProducerRecords(final TopologyTestDriver driver,
                                                                          final String topic,
                                                                          final Deserializer<K> keyDeserializer,
                                                                          final Deserializer<V> valueDeserializer) {
        final List<ProducerRecord<K, V>> result = new LinkedList<>();
        for (ProducerRecord<K, V> next = driver.readOutput(topic, keyDeserializer, valueDeserializer);
             next != null;
             next = driver.readOutput(topic, keyDeserializer, valueDeserializer)) {
            result.add(next);
        }
        return new ArrayList<>(result);
    }