Status
Current state: Under Discussion
Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
JIRA:
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KAFKA-8233Getting issue details...
STATUS
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
When using TopologyTestDriver you need to call ConsumerRecordFactory to create ConsumerRecord passed into pipeInput method to write to topic. Also when calling readOutput to consume from topic, you need to provide correct Deserializers each time.
You easily end up writing helper methods in your test classes, but this can be avoided when adding generic input and output topic classes wrapping existing functionality.
Public Interfaces
package org.apache.kafka.streams.test; public class TestInputTopic<K, V> { //Constructors with serializers TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serializer<K> keySerializer, final Serializer<V> valueSerializer); TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serializer<K> keySerializer, final Serializer<V> valueSerializer, final long startTimestampMs); TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serializer<K> keySerializer, final Serializer<V> valueSerializer, final long startTimestampMs, final long autoAdvanceMs); //Constructors with serdes TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serde<K> keySerde, final Serde<V> valueSerde); TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serde<K> keySerde, final Serde<V> valueSerde, final long startTimestampMs); TestInputTopic(final TopologyTestDriver driver, final String topicName, final Serde<K> keySerde, final Serde<V> valueSerde, final long startTimestampMs, final long autoAdvanceMs); //Methods to pipe single record void pipeInput(V value); void pipeInput(K key, V value); void pipeInput(V value, long timestampMs); void pipeInput(K key, V value, long timestampMs); void pipeInput(K key, V value, Headers headers); void pipeInput(K key, V value, Headers headers, long timestampMs); void pipeKeyValueList(List<KeyValue<K, V>> keyValues); void pipeValueList(List<V> values); void pipeKeyValueList(List<KeyValue<K, V>> keyValues, long startTimestamp, long advanceMs); void pipeValueList(List<V> values, long startTimestamp, long advanceMs); }
package org.apache.kafka.streams.test; public class TestOutputTopic<K, V> { //Constructor with serializers TestOutputTopic(final TopologyTestDriver driver, final String topic, final Serde<K> keySerde, final Serde<V> valueSerde); //Constructor with serdes TestOutputTopic(final TopologyTestDriver driver, final String topic, final Deserializer<K> keyDeserializer, final Deserializer<V> valueDeserializer); //Methods to readOutput ProducerRecord<K, V> readRecord(); KeyValue<K, V> readKeyValue(); V readValue(); //Output as collection Map<K, V> readKeyValuesToMap(); List<KeyValue<K, V>> readKeyValuesToList(); //If KPI-451 is included <K, V> Iterable<ProducerRecord<K, V>> iterableRecords(); <K, V> Iterable<KeyValue<K, V>> iterableKeyValues(); <V> Iterable<V> iterableValues(); }
Proposed Changes
This improvement adds TestInputTopic class which wraps TopologyTestDriver and ConsumerRecordFactory methods as one class to be used to write to Input Topics and TestOutputTopic class which collects TopologyTestDriver reading methods and provide typesafe read methods.
public class SimpleTopicTest { private TopologyTestDriver testDriver; private TestInputTopic<String, String> inputTopic; private TestOutputTopic<String, String> outputTopic; @Before public void setup() { final StreamsBuilder builder = new StreamsBuilder(); TestStream app = new TestStream(); //Create Actual Stream Processing pipeline app.createStream(builder); testDriver = new TopologyTestDriver(builder.build(),app.config); inputTopic = new TestInputTopic<String, String>(testDriver, TestStream.INPUT_TOPIC, new Serdes.StringSerde(), new Serdes.StringSerde()); outputTopic = new TestOutputTopic<String, String>(testDriver, TestStream.OUTPUT_TOPIC, new Serdes.StringSerde(), new Serdes.StringSerde()); } @After public void tearDown() { testDriver.close(); } @Test public void testOneWord() { //Feed word "Hello" to inputTopic and no kafka key, timestamp is irrelevant in this case inputTopic.pipeInput("Hello"); assertThat(outputTopic.readValue()).isEqualTo("Hello"); //No more output in topic assertThat(outputTopic.readRecord()).isNull(); } }
- Examples in Testing Kafka Streams https://kafka.apache.org/22/documentation/streams/developer-guide/testing.html updated to use TestInputTopic and TestOutputTopic
Compatibility, Deprecation, and Migration Plan
This is only adding new classes. The tests utilizing directly TopologyTestDriver can still be used. There are no compatibility issues.
Rejected Alternatives
- This version contains both original methods to fetch group of output as List or Map and KIP-451: Make TopologyTestDriver output iterable is proposing similar with Iterable. The collection might be removed in favour of Iterable