Kartik Khare has a guide to help us write unit tests for our Apache Flink code:
Writing tests for process functions, that work with time, is quite similar to writing tests for stateful functions because you can also use test harness. However, you need to take care of another aspect, which is providing timestamps for events and controlling the current time of the application. By setting the current (processing or event) time, you can trigger registered timers, which will call the
onTimermethod of the function
Click through for demos and more details on the test harness.