Github user bowenli86 commented on the issue:
https://github.com/apache/flink/pull/5649
When I was developing KeyedProcessFunction, I initially wondered why
there's no tests for KeyedStream, and researched and realized that they were
actually mixed with DataStream tests.
I think having that clarity by separating those tests would be great. Well,
I also agree it doesn't hurt that much to keep them as-is. If you feel strongly
against it, I can close this PR
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