[jira] [Created] (FLINK-4552) Refactor WindowOperator/Trigger Tests

["Aljoscha Krettek (JIRA)" <ji...@apache.org>]

Aljoscha Krettek created FLINK-4552:
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             Summary: Refactor WindowOperator/Trigger Tests
                 Key: FLINK-4552
                 URL: https://issues.apache.org/jira/browse/FLINK-4552
             Project: Flink
          Issue Type: Improvement
          Components: Windowing Operators
            Reporter: Aljoscha Krettek
            Assignee: Aljoscha Krettek


Right now, tests for {{WindowOperator}}, {{WindowAssigner}}, {{Trigger}} and {{WindowFunction}} are all conflated in {{WindowOperatorTest}}. All of these test that a certain combination of a {{Trigger}}, {{WindowAssigner}} and {{WindowFunction}} produce the expected output.

We should modularize these tests and spread them out across multiple files, possibly one per trigger, for the triggers. Also, we should extend/change the tests in some key ways:
 - {{WindowOperatorTest}} test should just verify that the interaction between {{WindowOperator}} and the various other parts works as expected, that the correct methods on {{Trigger}} and {{WindowFunction}} are called at the expected time and that snapshotting, timers, cleanup etc. work correctly. These tests should also verify that the different state types and {{WindowFunctions}} work correctly.
 - {{Trigger}} tests should present elements to triggers and verify that they fire at the correct times. The actual output of the {{WindowFunction}} is not important for these tests. We should also test that triggers correctly clean up state and timers.
 - {{WindowAssigner}} tests should test each window assigner and also verify that, for example, the offset parameter of time-based windows works correctly.

There is already {{WindowingTestHarness}} but it is not used by tests, I think we can expand on that and provide more thorough test coverage while also making the tests more maintainable ({{WindowOperatorTest.java}} is nearing 3000 lines of code).



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