TopologyTestDriver
TopologyTestDriver is a Kafka Streams testing utility that runs a topology in memory without requiring a running Kafka cluster.
Kafka Streams in Action, Second Edition
TopologyTestDriver is a Kafka Streams test utility that runs a topology in memory and provides test input, output, and state-store access.
- How it is used
- Tests an entire Kafka Streams topology quickly without requiring a live Kafka broker.
- How deep it goes
- Covers setup, record injection, output assertions, state-store inspection, and timestamp-driven behavior, while deferring broker integration to Testcontainers.
- Examples
- Uses a yelling topology, a stateful poker-score reducer, ordered records, state-store assertions, and timestamped window-processing records.
- What you can do after
- Diagnose/debug with it by piping deterministic records through a topology and comparing emitted results and state-store contents.
Read how Kafka Streams in Action, Second Edition explains TopologyTestDriver →
Kafka for Architects
TopologyTestDriver is a Kafka Streams testing class that executes and verifies a topology without requiring a running Kafka cluster.
- How it is used
- Validates complete Kafka Streams topologies without requiring a running Kafka cluster.
- How deep it goes
- Explains test topics, serialization, output assertions, simulated time, and state inspection; defers real-cluster communication to integration testing.
- Examples
- Uses TestInputTopic and TestOutputTopic to pipe serialized records, verify outputs, advance time, and inspect intermediate state.
- What you can do after
- Evaluate Kafka Streams transformations and stateful behavior without deploying a Kafka cluster.
Related concepts
- processor topologyuses · A processor topology is a directed graph of source, processor, and sink nodes that defines how records flow through a stream-processing application.
- state storeuses · A state store is a storage component that maintains application or processing state and provides mechanisms to access or update it.
- Kafka Streamsused by · Kafka Streams is a client library for building applications that continuously process data from and write data to Apache Kafka topics.
- TestInputTopicproduces · TestInputTopic is a Kafka Streams testing utility that represents an input topic and supplies records to a topology under test.
- TestOutputTopicproduces · TestOutputTopic is a Kafka Streams testing utility that represents an output topic and reads records produced by a topology under test.
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