Test-driven development (TDD) improves code reliability by writing tests before coding, providing immediate feedback, and identifying defects early. In the context of Apache Kafka's complex streaming system, the integration of Quarkus, Redpanda, and Testcontainers simplifies TDD and continuous integration (CI). Quarkus facilitates immediate testing by allowing code changes without restarting applications, while Testcontainers ensures consistency in testing environments by using Docker containers. Redpanda, a lightweight alternative to Kafka, offers faster and more resource-efficient testing, crucial for both development and CI environments. The demo application illustrates how these tools work together to filter customer data, showcasing the TDD approach where tests define the desired behavior and automated CI pipelines ensure code changes don't introduce new bugs. The use of Testcontainers and Redpanda in TDD and CI environments eliminates the need for separate Kafka instances, saving resources and time while maintaining consistency between local and CI test environments.