main point of testFlinkKafkaProducerFailTransactionCoordinatorBeforeNotify is to fail transaction coordinator (by using kafkaProducer.getTransactionCoordinatorId(); ) and we expect that this will cause failure of Flink job. However that's not always the case. Maybe because transaction coordinator can be re-elected before KafkaProducer even notices it or for whatever the reason, sometimes the failure is not happening.
Because of a bug in the test, if failure hasn't happened, the test will not fail.
Generally speaking this test is invalid and should be dropped.