Confluent - Developer for Apache Kafka Study Guide

5: Application Testing

This chapter builds the developer-side testing surface for Kafka client applications, mapping the producer, consumer, and Streams patterns from earlier chapters onto in-process test harnesses that run without a live broker. It walks `TopologyTestDriver` for Streams topologies, `MockProducer` and `MockConsumer` for client logic, embedded clusters and Testcontainers for integration coverage, and the discipline needed to keep every one of those tests deterministic under wall-clock time, partitioning, and rebalance events.