Github user pnowojski commented on the issue:
https://github.com/apache/flink/pull/6081
@yanghua why is it difficult? Can not you create more or less similar test
to @GJL's `testSetsUserCodeClassLoader` from here:
https://github.com/apache/flink/pull/4980/files. With couple side notes:
1. build `MockEnvironment` using `MockEnvironmentBuilder` with a custom
user class loader - do not use mockito for that
2. create a stream task (reusing one of the implementation in
`StreamTaskTest.java` or create a new one)
3. register a timer service, wait for it's triggering and assert the user
class loader in `ProcessingTimeCallback#onProcessingTime`
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