POC - Testing flink apps

Currently at work there's a team developing flinks apps, but testing is only in integration. I'd like to be able to do some unit tests as Integration ones, spinning up Flink app and doing an e2e testing every build (even local)

The app

Simple app with the following specification:

• Stream application
• Reading from Kafka topic
• Simple logic (add a prefix/suffix?) applied to the stream elements
• POST the result to:
  • a third party system (REST service)
  • a Kafka topic

Goals

Integration tests should:

• GIVEN Set data to be streamed via Kafka - write the initial data
• WHEN - flink app is started
• THEN - REST service is hit with a POST, modified data

Initial tools to use

• JUnit 5
• Kafka - spin up a docker container/java code?
• Wiremock as REST service - see Vefiry feature

Lessons learnt

• TODO : add any lessons learn in the way