david-parkk opened a new pull request, #22651:
URL: https://github.com/apache/kafka/pull/22651
## Summary
`KafkaConsumerTest.fetchResponseWithUnexpectedPartitionIsIgnored` was
annotated with `@EnumSource(GroupProtocol.class)`, but the CONSUMER protocol
case passed for the wrong reason.
The CONSUMER protocol uses `FetchRequestManager` and relies on
`ConsumerGroupHeartbeat` for rebalancing. Since the test does not set up
heartbeat-based rebalancing, partition assignment never completes and 0 records
are returned — not because `FetchSessionHandler` correctly rejected the
response.
## Analysis
While writing the CONSUMER protocol test, we first attempted to use
`AsyncKafkaConsumerTest` as a reference. However, it was not suitable because
`fetchCollector` is replaced with a Mock, meaning `FetchSessionHandler`'s
actual rejection logic is never exercised.
We also found that naively adding the CONSUMER case to `KafkaConsumerTest`
does not work either. The test uses `prepareResponse()` for the Join and Sync
group requests, but these responses were never consumed — because the CONSUMER
protocol does not go through the classic Join/Sync rebalance flow. As a result,
the fetch phase was never reached. `FetchRequestManagerTest` is the correct
location for this test, as it directly runs `FetchSessionHandler` without
mocking.
## Changes
- **`KafkaConsumerTest`**: Restrict
`fetchResponseWithUnexpectedPartitionIsIgnored` to `CLASSIC` protocol only,
where the existing setup correctly exercises `FetchSessionHandler`'s unexpected
partition rejection logic.
- **`FetchRequestManagerTest`**: Add
`testFetchResponseWithUnexpectedPartitionIsIgnored` to properly cover the
CONSUMER protocol path. The test verifies that when a `FetchResponse` contains
a partition not included in the `FetchRequest`, `FetchSessionHandler` rejects
the entire response and no records are returned to the consumer.
---
I'm happy to make any adjustments based on your feedback. Thank you to the
maintainers for taking the time to review this contribution!
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