public void produceMessage(String topicName, int partitionId, String key, String val) {
    producer.send(new ProducerRecord<>(topicName, partitionId, key, val));
    producer.flush();
    LOG.info("Sent key: {} val: {} to topic: {} on partition: {}", key, val, topicName, partitionId);
  }
Produces a message to the provided topic partition.
@param topicName the topic to produce messages to
@param partitionId the topic partition to produce messages to
@param key the key in the message
@param val the value in the message
samza-test/src/test/java/org/apache/samza/test/framework/StreamApplicationIntegrationTestHarness.java