The December 2019 release of Apache Kafka 2.4.0 saw usability improvements in TopologyTestDriver, with the addition of new TestInputTopic and TestOutputTopic classes. These offer typesafe methods to easily produce and consume messages for your Kafka Streams tests. In this post we’ll explore these new classes in the context of Avro messages, which requires a small trick to get working.

Distributed tracing is a method used to profile and monitor applications, especially those built using a microservices architecture. Distributed tracing helps pinpoint where failures occur and what causes poor performance.^[1] Applied to Kafka Streams it allows us to trace and visualize our messages by propagating diagnostic information within message headers.