.. title:: Test Kafka Streams Code in Confluent Platform .. meta:: :description: Learn how to test your Kafka Streams applications in Confluent Platform. .. _streams_developer-testing: Test |kstreams| Code in |cp| ---------------------------- |kstreams| provides a test driver and helper classes for testing your applications. Importing the Test Utilities ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ To test a |kstreams| application, |ak-tm| provides a test-utils artifact that can be added as regular dependency to your test code base. Here is an example ``pom.xml`` snippet when using Maven: .. codewithvars:: xml org.apache.kafka kafka-streams-test-utils |kafka_release| test .. _streams_developer-testing-topology_test_driver: Testing a Streams Application ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ When you create a Streams application, you create a ``Topology``, either using the :ref:`StreamsBuilder DSL ` or using the low-level :ref:`Processor API `. Normally, you run the topology using the ``KafkaStreams`` class, which connects to your broker and begins processing when you call ``start()``. For testing, though, running a broker and making sure to clean up state between tests adds a lot of complexity and time. Streams provides the ``TopologyTestDriver`` in the ``kafka-streams-test-utils`` package as a drop-in replacement for the ``KafkaStreams`` class. It has no external system dependencies, and it also processes input synchronously, so you can verify the results immediately after providing input. There are hooks for verifying data sent to output topics, and you can also query state stores maintained by your application under test. To set it up: .. sourcecode:: java // Processor API Topology topology = new Topology(); topology.addSource("sourceProcessor", "input-topic"); topology.addProcessor("processor", ..., "sourceProcessor"); topology.addSink("sinkProcessor", "output-topic", "processor"); // or // using DSL StreamsBuilder builder = new StreamsBuilder(); builder.stream("input-topic").filter(...).to("output-topic"); Topology topology = builder.build(); // create test driver TopologyTestDriver testDriver = new TopologyTestDriver(topology); To pipe records through the test-driver, you can create a ``TestInputTopic`` for each input topic of your topology: .. sourcecode:: java TestInputTopic inputTopic = testDriver.createInputTopic( "input-topic", new StringSerializer(), new IntegerSerializer()); inputTopic.pipeInput("key", 42); For result verification, you first create a ``TestOutputTopic``: .. sourcecode:: java TestOutputTopic outputTopic = testDriver.createOutputTopic( "result-topic", new StringDeserializer(), new LongDeserializer()); You can either verify only the record value, the key and the values, or a full ``TestRecord`` that includes timestamp and header information. Consuming an output topic as a *table* is also possible using ``TestOutputTopic#readKeyValuesToMap()``. .. sourcecode:: java // user assertion library of your choice to verify output assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); ------------------ ``TopologyTestDriver`` supports punctuations, too. Event-time punctuations are triggered automatically based on the processed records' timestamps. Wall-clock-time punctuations can also be triggered by advancing the test driver's wall-clock time. The driver's wall-clock time must be advanced manually (this is for test stability). .. sourcecode:: java testDriver.advanceWallClockTime(Duration.ofMillis(20L)); // supposing that a scheduled punctuator would emit this record... assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("triggered-key", "triggered-value"))); ------------------ Additionally, state stores are accessible via the test driver before or after a test. Accessing stores before a test is useful to pre-populate a store with some initial values. After data was processed, expected updates to the store can be verified. .. sourcecode:: java KeyValueStore store = testDriver.getKeyValueStore("store-name"); assertEquals("some value", store.get("some key")); ------------------ Always close the test driver at the end to make sure all resources are released properly. .. sourcecode:: java testDriver.close(); Example """"""" The following example demonstrates how to use the test driver and helper classes. The example creates a topology that computes the maximum value per key using a key-value-store. While processing, no output is generated, but only the store is updated. Output is only sent downstream based on event-time and wall-clock punctuations. .. tip:: For a full end-to-end example, see the blog post, `Testing Kafka Streams Using TestInputTopic and TestOutputTopic `__ and the corresponding GitHub repo at `kafka-streams-test-topics `__. .. sourcecode:: java private TopologyTestDriver testDriver; private TestInputTopic inputTopic; private TestOutputTopic outputTopic; private KeyValueStore store; private Serde stringSerde = new Serdes.StringSerde(); private Serde longSerde = new Serdes.LongSerde(); @Before public void setup() { final Topology topology = new Topology(); topology.addSource("sourceProcessor", "input-topic"); topology.addProcessor("aggregator", new CustomMaxAggregatorSupplier(), "sourceProcessor"); topology.addStateStore( Stores.keyValueStoreBuilder( Stores.inMemoryKeyValueStore("aggStore"), Serdes.String(), Serdes.Long()).withLoggingDisabled(), // need to disable logging to allow store pre-populating "aggregator"); topology.addSink("sinkProcessor", "result-topic", "aggregator"); // create test driver testDriver = new TopologyTestDriver(topology); // setup test topics inputTopic = testDriver.createInputTopic("input-topic", stringSerde.serializer(), longSerde.serializer()); outputTopic = testDriver.createOutputTopic("result-topic", stringSerde.deserializer(), longSerde.deserializer()); // pre-populate store store = testDriver.getKeyValueStore("aggStore"); store.put("a", 21L); } @After public void tearDown() { testDriver.close(); } @Test public void shouldFlushStoreForFirstInput() { inputTopic.pipeInput("a", 1L); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); assertThat(outputTopic.isEmpty(), is(true)); } @Test public void shouldNotUpdateStoreForSmallerValue() { inputTopic.pipeInput("a", 1L); assertThat(store.get("a"), equalTo(21L)); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); assertThat(outputTopic.isEmpty(), is(true)); } @Test public void shouldNotUpdateStoreForLargerValue() { inputTopic.pipeInput("a", 42L); assertThat(store.get("a"), equalTo(42L)); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 42L))); assertThat(outputTopic.isEmpty(), is(true)); } @Test public void shouldUpdateStoreForNewKey() { inputTopic.pipeInput("b", 21L); assertThat(store.get("b"), equalTo(21L)); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("b", 21L))); assertThat(outputTopic.isEmpty(), is(true)); } @Test public void shouldPunctuateIfEvenTimeAdvances() { final Instant recordTime = Instant.now(); inputTopic.pipeInput("a", 1L, recordTime); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); inputTopic.pipeInput("a", 1L, recordTime); assertThat(outputTopic.isEmpty(), is(true)); inputTopic.pipeInput("a", 1L, recordTime.plusSeconds(10L)); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); assertThat(outputTopic.isEmpty(), is(true)); } @Test public void shouldPunctuateIfWallClockTimeAdvances() { testDriver.advanceWallClockTime(Duration.ofSeconds(60)); assertThat(outputTopic.readKeyValue(), equalTo(new KeyValue<>("a", 21L))); assertThat(outputTopic.isEmpty(), is(true)); } public static class CustomMaxAggregatorSupplier implements ProcessorSupplier { @Override public Processor get() { return new CustomMaxAggregator(); } } public static class CustomMaxAggregator implements Processor { ProcessorContext context; private KeyValueStore store; @SuppressWarnings("unchecked") @Override public void init(final ProcessorContext context) { this.context = context; context.schedule(Duration.ofSeconds(60), PunctuationType.WALL_CLOCK_TIME, time -> flushStore()); context.schedule(Duration.ofSeconds(10), PunctuationType.STREAM_TIME, time -> flushStore()); store = (KeyValueStore) context.getStateStore("aggStore"); } @Override public void process(final String key, final Long value) { final Long oldValue = store.get(key); if (oldValue == null || value > oldValue) { store.put(key, value); } } private void flushStore() { final KeyValueIterator it = store.all(); while (it.hasNext()) { final KeyValue next = it.next(); context.forward(next.key, next.value); } } @Override public void close() {} } .. _streams_developer-testing-mock_processor_context: Unit Testing for Processors ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Using the :ref:`Processor API `, you can define custom ``Processor``, ``Transformer``, or ``ValueTransformer`` implementations. Because these classes forward their results to the ``ProcessorContext`` rather than returning them, unit testing requires a mocked context capable of capturing forwarded data for inspection. Streams provides ``MockProcessorContext`` in ``kafka-streams-test-utils`` for this purpose. To begin with, instantiate your processor and initialize it with the mock context: .. sourcecode:: java final Processor processorUnderTest = ...; final MockProcessorContext context = new MockProcessorContext(); processorUnderTest.init(context); If you need to pass configuration to your processor or set the default serdes, you can create the mock with config: .. sourcecode:: java final Properties config = new Properties(); config.put(StreamsConfig.APPLICATION_ID_CONFIG, "unit-test"); config.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, ""); config.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass()); config.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.Long().getClass()); config.put("some.other.config", "some config value"); final MockProcessorContext context = new MockProcessorContext(config); The mock captures any values that your processor forwards. You can make assertions on them: .. sourcecode:: java processorUnderTest.process("key", "value"); final Iterator forwarded = context.forwarded().iterator(); assertEquals(forwarded.next().keyValue(), new KeyValue<>(..., ...)); assertFalse(forwarded.hasNext()); // you can reset forwards to clear the captured data. This may be helpful in constructing longer scenarios. context.resetForwards(); assertEquals(context.forwarded().size(), 0); If your processor forwards to specific child processors, you can query the context for captured data by child name: .. sourcecode:: java final List captures = context.forwarded("childProcessorName"); The mock also captures whether your processor has called ``commit()`` on the context: .. sourcecode:: java assertTrue(context.committed()); // commit captures can also be reset. context.resetCommit(); assertFalse(context.committed()); In case your processor logic depends on the record metadata (topic, partition, offset, or timestamp), you can set them on the context, either all together or individually: .. sourcecode:: java context.setRecordMetadata("topicName", /*partition*/ 0, /*offset*/ 0L, /*timestamp*/ 0L); context.setTopic("topicName"); context.setPartition(0); context.setOffset(0L); context.setTimestamp(0L); Once these are set, the context continues returning the same values, until you set new ones. -------------- In case your punctuator is stateful, the mock context allows you to register state stores. You are encouraged to use a simple in-memory store of the appropriate type (``KeyValue``, ``Windowed``, or ``Session``), since the mock context does *not* manage changelogs, state directories, etc. .. sourcecode:: java final KeyValueStore store = Stores.keyValueStoreBuilder( Stores.inMemoryKeyValueStore("myStore"), Serdes.String(), Serdes.Integer() ) .withLoggingDisabled() // Changelog is not supported by MockProcessorContext. .build(); store.init(context, store); context.register(store, /*parameter unused in mock*/ null); -------------- Processors can schedule punctuators to handle periodic tasks. The mock context does *not* automatically execute punctuators, but it does capture schedule calls so that you can unit test the punctuator scheduling behavior yourself: .. sourcecode:: java final MockProcessorContext.CapturedPunctuator capturedPunctuator = context.scheduledPunctuators().get(0); final long interval = capturedPunctuator.getIntervalMs(); final PunctuationType type = capturedPunctuator.getType(); final boolean cancelled = capturedPunctuator.cancelled(); final Punctuator punctuator = capturedPunctuator.getPunctuator(); punctuator.punctuate(/*timestamp*/ 0L); If you need to write tests involving automatic firing of scheduled punctuators, you should use the ``TopologyTestDriver`` on a simple topology containing your processor. Suggested Resources ^^^^^^^^^^^^^^^^^^^ - `Learn: Tools and Resources for Testing Apache Kafka `__ - `Blog post: Testing Kafka Streams Using TestInputTopic and TestOutputTopic `__ - `Blog post: Getting Your Feet Wet with Stream Processing – Part 2: Testing Your Streaming Application `__ .. include:: ../../.hidden/docs-common/home/includes/ak-share.rst