TopologyTestDriver (kafka 2.2.0 API)

java.lang.Object
- org.apache.kafka.streams.TopologyTestDriver

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable
```
@InterfaceStability.Evolving
public class TopologyTestDriver
extends java.lang.Object
implements java.io.Closeable
```
This class makes it easier to write tests to verify the behavior of topologies created with Topology or StreamsBuilder. You can test simple topologies that have a single processor, or very complex topologies that have multiple sources, processors, sinks, or sub-topologies. Best of all, the class works without a real Kafka broker, so the tests execute very quickly with very little overhead.
Using the TopologyTestDriver in tests is easy: simply instantiate the driver and provide a Topology (cf. StreamsBuilder.build()) and configs, use the driver to supply an input message to the topology, and then use the driver to read and verify any messages output by the topology.
Although the driver doesn't use a real Kafka broker, it does simulate Kafka consumers and producers that read and write raw byte[] messages. You can either deal with messages that have byte[] keys and values or you use ConsumerRecordFactory and OutputVerifier that work with regular Java objects instead of raw bytes.
Driver setup
In order to create a TopologyTestDriver instance, you need a Topology and a config. The configuration needs to be representative of what you'd supply to the real topology, so that means including several key properties (cf. StreamsConfig). For example, the following code fragment creates a configuration that specifies a local Kafka broker list (which is needed but not used), a timestamp extractor, and default serializers and deserializers for string keys and values:
```
 Properties props = new Properties();
 props.setProperty(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9091");
 props.setProperty(StreamsConfig.DEFAULT_TIMESTAMP_EXTRACTOR_CLASS_CONFIG, CustomTimestampExtractor.class.getName());
 props.setProperty(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
 props.setProperty(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
 Topology topology = ...
 TopologyTestDriver driver = new TopologyTestDriver(topology, props);
 
```
Processing messages

Your test can supply new input records on any of the topics that the topology's sources consume. This test driver simulates single-partitioned input topics. Here's an example of an input message on the topic named input-topic:
```
 ConsumerRecordFactory factory = new ConsumerRecordFactory(strSerializer, strSerializer);
 driver.pipeInput(factory.create("input-topic","key1", "value1"));
 
```
When #pipeInput() is called, the driver passes the input message through to the appropriate source that consumes the named topic, and will invoke the processor(s) downstream of the source. If your topology's processors forward messages to sinks, your test can then consume these output messages to verify they match the expected outcome. For example, if our topology should have generated 2 messages on output-topic-1 and 1 message on output-topic-2, then our test can obtain these messages using the readOutput(String, Deserializer, Deserializer) method:
```
 ProducerRecord<String, String> record1 = driver.readOutput("output-topic-1", strDeserializer, strDeserializer);
 ProducerRecord<String, String> record2 = driver.readOutput("output-topic-1", strDeserializer, strDeserializer);
 ProducerRecord<String, String> record3 = driver.readOutput("output-topic-2", strDeserializer, strDeserializer);
 
```
Again, our example topology generates messages with string keys and values, so we supply our string deserializer instance for use on both the keys and values. Your test logic can then verify whether these output records are correct. Note, that calling ProducerRecord.equals(Object) compares all attributes including key, value, timestamp, topic, partition, and headers. If you only want to compare key and value (and maybe timestamp), using OutputVerifier instead of ProducerRecord.equals(Object) can simplify your code as you can ignore attributes you are not interested in.
Note, that calling pipeInput() will also trigger event-time base punctuation callbacks. However, you won't trigger wall-clock type punctuations that you must trigger manually via advanceWallClockTime(long).
Finally, when completed, make sure your tests close() the driver to release all resources and processors.
Processor state

Some processors use Kafka state storage, so this driver class provides the generic getStateStore(String) as well as store-type specific methods so that your tests can check the underlying state store(s) used by your topology's processors. In our previous example, after we supplied a single input message and checked the three output messages, our test could also check the key value store to verify the processor correctly added, removed, or updated internal state. Or, our test might have pre-populated some state before submitting the input message, and verified afterward that the processor(s) correctly updated the state.
See Also:

ConsumerRecordFactory, OutputVerifier

Constructor Summary

Constructors
Constructor and Description
`TopologyTestDriver(Topology topology, java.util.Properties config)` Create a new test diver instance.
`TopologyTestDriver(Topology topology, java.util.Properties config, long initialWallClockTimeMs)` Create a new test diver instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`advanceWallClockTime(long advanceMs)` Advances the internally mocked wall-clock time.
`void`	`close()` Close the driver, its topology, and all processors.
`java.util.Map<java.lang.String,StateStore>`	`getAllStateStores()` Get all `StateStores` from the topology.
`<K,V> KeyValueStore<K,V>`	`getKeyValueStore(java.lang.String name)` Get the `KeyValueStore` with the given name.
`<K,V> SessionStore<K,V>`	`getSessionStore(java.lang.String name)` Get the `SessionStore` with the given name.
`StateStore`	`getStateStore(java.lang.String name)` Get the `StateStore` with the given name.
`<K,V> WindowStore<K,V>`	`getWindowStore(java.lang.String name)` Get the `WindowStore` with the given name.
`java.util.Map<MetricName,? extends Metric>`	`metrics()` Get read-only handle on global metrics registry.
`void`	`pipeInput(ConsumerRecord<byte[],byte[]> consumerRecord)` Send an input message with the given key, value, and timestamp on the specified topic to the topology and then commit the messages.
`void`	`pipeInput(java.util.List<ConsumerRecord<byte[],byte[]>> records)` Send input messages to the topology and then commit each message individually.
`ProducerRecord<byte[],byte[]>`	`readOutput(java.lang.String topic)` Read the next record from the given topic.
`<K,V> ProducerRecord<K,V>`	`readOutput(java.lang.String topic, Deserializer<K> keyDeserializer, Deserializer<V> valueDeserializer)` Read the next record from the given topic.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - TopologyTestDriver
```
public TopologyTestDriver(Topology topology,
                          java.util.Properties config)
```
    Create a new test diver instance. Initialized the internally mocked wall-clock time with current system time.
    
    Parameters:
    
    topology - the topology to be tested
    
    config - the configuration for the topology
  - TopologyTestDriver
```
public TopologyTestDriver(Topology topology,
                          java.util.Properties config,
                          long initialWallClockTimeMs)
```
    Create a new test diver instance.
    
    Parameters:
    
    topology - the topology to be tested
    
    config - the configuration for the topology
    
    initialWallClockTimeMs - the initial value of internally mocked wall-clock time
- Method Detail
  - metrics
```
public java.util.Map<MetricName,? extends Metric> metrics()
```
    Get read-only handle on global metrics registry.
    
    Returns:
    
    Map of all metrics.
  - pipeInput
```
public void pipeInput(ConsumerRecord<byte[],byte[]> consumerRecord)
```
    Send an input message with the given key, value, and timestamp on the specified topic to the topology and then commit the messages.
    
    Parameters:
    
    consumerRecord - the record to be processed
  - pipeInput
```
public void pipeInput(java.util.List<ConsumerRecord<byte[],byte[]>> records)
```
    Send input messages to the topology and then commit each message individually.
    
    Parameters:
    
    records - a list of records to be processed
  - advanceWallClockTime
```
public void advanceWallClockTime(long advanceMs)
```
    Advances the internally mocked wall-clock time. This might trigger a wall-clock type punctuations.
    
    Parameters:
    
    advanceMs - the amount of time to advance wall-clock time in milliseconds
  - readOutput
```
public ProducerRecord<byte[],byte[]> readOutput(java.lang.String topic)
```
    Read the next record from the given topic. These records were output by the topology during the previous calls to pipeInput(ConsumerRecord).
    
    Parameters:
    
    topic - the name of the topic
    
    Returns:
    
    the next record on that topic, or null if there is no record available
  - readOutput
```
public <K,V> ProducerRecord<K,V> readOutput(java.lang.String topic,
                                            Deserializer<K> keyDeserializer,
                                            Deserializer<V> valueDeserializer)
```
    Read the next record from the given topic. These records were output by the topology during the previous calls to pipeInput(ConsumerRecord).
    
    Parameters:
    
    topic - the name of the topic
    
    keyDeserializer - the deserializer for the key type
    
    valueDeserializer - the deserializer for the value type
    
    Returns:
    
    the next record on that topic, or null if there is no record available
  - getAllStateStores
```
public java.util.Map<java.lang.String,StateStore> getAllStateStores()
```
    Get all StateStores from the topology. The stores can be a "regular" or global stores.
    This is often useful in test cases to pre-populate the store before the test case instructs the topology to process an input message, and/or to check the store afterward.
    Note, that StateStore might be null if a store is added but not connected to any processor.
    
    Returns:
    
    all stores my name
    
    See Also:
    
    getStateStore(String), getKeyValueStore(String), getWindowStore(String), getSessionStore(String)
  - getStateStore
```
public StateStore getStateStore(java.lang.String name)
```
    Get the StateStore with the given name. The store can be a "regular" or global store.
    This is often useful in test cases to pre-populate the store before the test case instructs the topology to process an input message, and/or to check the store afterward.
    
    Parameters:
    
    name - the name of the store
    
    Returns:
    
    the state store, or null if no store has been registered with the given name
    
    See Also:
    
    getAllStateStores(), getKeyValueStore(String), getWindowStore(String), getSessionStore(String)
  - getKeyValueStore
```
public <K,V> KeyValueStore<K,V> getKeyValueStore(java.lang.String name)
```
    Get the KeyValueStore with the given name. The store can be a "regular" or global store.
    This is often useful in test cases to pre-populate the store before the test case instructs the topology to process an input message, and/or to check the store afterward.
    
    Parameters:
    
    name - the name of the store
    
    Returns:
    
    the key value store, or null if no KeyValueStore has been registered with the given name
    
    See Also:
    
    getAllStateStores(), getStateStore(String), getWindowStore(String), getSessionStore(String)
  - getWindowStore
```
public <K,V> WindowStore<K,V> getWindowStore(java.lang.String name)
```
    Get the WindowStore with the given name. The store can be a "regular" or global store.
    This is often useful in test cases to pre-populate the store before the test case instructs the topology to process an input message, and/or to check the store afterward.
    
    Parameters:
    
    name - the name of the store
    
    Returns:
    
    the key value store, or null if no WindowStore has been registered with the given name
    
    See Also:
    
    getAllStateStores(), getStateStore(String), getKeyValueStore(String), (String)
  - getSessionStore
```
public <K,V> SessionStore<K,V> getSessionStore(java.lang.String name)
```
    Get the SessionStore with the given name. The store can be a "regular" or global store.
    This is often useful in test cases to pre-populate the store before the test case instructs the topology to process an input message, and/or to check the store afterward.
    
    Parameters:
    
    name - the name of the store
    
    Returns:
    
    the key value store, or null if no SessionStore has been registered with the given name
    
    See Also:
    
    getAllStateStores(), getStateStore(String), getKeyValueStore(String), getWindowStore(String)
  - close
```
public void close()
```
    Close the driver, its topology, and all processors.
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Specified by:
    
    close in interface java.lang.AutoCloseable

Class TopologyTestDriver

Driver setup

Processing messages

Processor state

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

TopologyTestDriver

TopologyTestDriver

Method Detail

metrics

pipeInput

pipeInput

advanceWallClockTime

readOutput

readOutput

getAllStateStores

getStateStore

getKeyValueStore

getWindowStore

getSessionStore

close