Need some pointers to writing (real) tests

[Jaikiran Pai]

I have been looking at some unassigned JIRAs to work on during some 
spare time and found this one 
https://issues.apache.org/jira/browse/KAFKA-1837. As I note in that 
JIRA, I can see why this happens and have a potential fix for it. But to 
first reproduce the issue and then verify the fix, I have been 
attempting a testcase (in the clients). Some of the tests that are 
already present (like SenderTest) use MockProducer which won't be 
relevant in testing this issue, from what I see.

So I need some inputs or pointers to create a test which will use the 
real KafkaProducer/Sender/NetworkClient. My initial attempt at this uses 
the TestUtils to create a (dummy) cluster, and that one fails for 
obvious reasons (the client not receiving a metadata update over the 
wire from the server):

    @Test
    public void testFailedSend() throws Exception {
        final TopicPartition tp = new TopicPartition("test", 0);
        final String producedValue = "foobar";
        final ProducerRecord product = new ProducerRecord(tp.topic(), 
producedValue);
        final Cluster cluster = TestUtils.singletonCluster("test", 1);
        final Node node = this.cluster.nodes().get(0);
        final Properties kakfaProducerConfigs = new Properties();
kakfaProducerConfigs.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, 
node.host() + ":" + node.port());
kakfaProducerConfigs.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, 
StringSerializer.class.getName());
kakfaProducerConfigs.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, 
StringSerializer.class.getName());
        final Producer producer = new KafkaProducer(kakfaProducerConfigs);

        // This times out waiting for a metadata update from the server 
for the cluster (because there isn't really any real server around)
        final Future<RecordMetadata> futureAck = producer.send(product);
        ....


Any pointers to existing tests?

-Jaikiran