Testing Kafka Streams Topologies

Every time we add or change the logic in our Kafka Streams topology, we should verify that our changes have the correct outcomes. This verification can be done by:

1. Starting a Kafka cluster

2. Running the entire application

3. Publishing input messages using the producer CLI

4. Reading the output message using the consumer CLI

While we should do this at least once or twice to verify all the parts of the system are playing correctly together, ...