RFR: 8336332: Rework tests to avoid unrelated stderr output [v11]

[Kevin Rushforth]

On Thu, 18 Sep 2025 18:50:04 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> This PR removes unrelated `stderr` output in the headless test logs by redirecting it to an in-memory buffer.  Exceptions found in the buffer can be checked against the expected list.
>> 
>> In the case when any mismatch is detected, whether the type or the number of exceptions of particular type, the accumulated buffer gets dumped to `stderr` and the test fails.
>> 
>> ## How To
>> 
>> To redirect stderr and later check the exceptions, surround your code with
>> 
>> `OutputRedirect.suppressStderr()` and either `OutputRedirect.checkStderr()` or `OutputRedirect.checkAndRestoreStderr()` (ideally, in the `finally` block).
>> 
>> To simply undo redirection, without checking, call  `OutputRedirect.restoreStderr()`.
>> 
>> To add the check to all the tests in the file, one can call the above mentioned methods inside  `@BeforeEach` and `@AfterEach`.
>> 
>> ## Changes
>> 
>> - added `OutputRedirect` facility
>> 
>> ## Miscellaneous
>> 
>> `ErrorLoggingUtiltity` name will be fixed in a followup https://bugs.openjdk.org/browse/JDK-8367995
>
> Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   run and wait

Shapshot1Test still fails for me. This time the exceptions are being captured in the print stream, but the parsing of the output reports 2 exceptions instead of the expected 1:


    Mismatch in thrown exceptions:
      expected={java.lang.ClassCastException=1}
      observed={java.lang.ClassCastException=1, Exception=1}

tests/system/src/test/java/test/javafx/scene/Snapshot1Test.java line 253:

> 251: 
> 252:             assertEquals(0, latch.getCount());
> 253:         } finally {

Since the ClassCast exception happens after the latch countdown, I recommend a sleep (of, say, 100 msec) after checking that the latch count is 0.

tests/system/src/test/java/test/javafx/scene/Snapshot1Test.java line 382:

> 380: 
> 381:             assertEquals(0, latch.getCount());
> 382:         } finally {

Same here: a short sleep after the assertEquals.

-------------

PR Review: https://git.openjdk.org/jfx/pull/1897#pullrequestreview-3241971053
PR Review Comment: https://git.openjdk.org/jfx/pull/1897#discussion_r2361081138
PR Review Comment: https://git.openjdk.org/jfx/pull/1897#discussion_r2361083383