RFR: 8301767: Convert virtual thread tests to JUnit [v2]

[Jaikiran Pai]

On Wed, 8 Feb 2023 08:14:33 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> The non-hotspot tests integrated with JEP 425/428 were mostly TestNG tests. We'd like to convert these JUnit in the main line in advance of other updates to these tests in 21.  The changes are mostly mechanical and trivial:
>> 
>> - BeforeClass/AfterClass changed to static BeforeAll/AfterAll methods
>> - Tests using data providers are changed to parameterized tests
>> - The order of the parameters to assertEquals are swapped so that the expected result is the first parameter
>> - Usages of expectThrows are changed to assertThrows
>> - Tests that threw SkipException are changed to the Assumptions API
>> 
>> There are a small number of drive-by changes to the tests, nothing significant, e.g.
>> 
>> - GetStackTrace and ParkWithFixedThreadPool changed from "@run testng" to "@run main" as they aren't TestNG tests.
>> - A few of the tests in StructuredTaskScopeTest for joinXXX are changed to use a CountDownLatch rather than sleeping, as the original tests weren't very robust.
>
> Alan Bateman has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:
> 
>  - Merge
>  - Merge
>  - Fix typos in comments
>  - GetStackTrace.java test missing @requires vm.continuations
>  - Initial commit

test/jdk/java/lang/Thread/virtual/GetStackTrace.java line 31:

> 29:  * @enablePreview
> 30:  * @modules java.base/java.lang:+open
> 31:  * @run main GetStackTrace

That's interesting - so this test was marked as a testng test previously, but had not test methods in it. I had a look at the test run history of this one and I see that the test execution results in:

> java/lang/Thread/virtual/GetStackTrace.java
> Total tests run: 0, Passes: 0, Failures: 0, Skips: 0

I wonder if testng (and junit) can be configured to fail the test if no test methods were present, to flag such mistakes.

Keeping that aside, the change to make this `@run main` looks fine.

As for adding the `@requires vm.continuations`, I'm not familiar with its expectations. Looking at the test case, it just captures stacktraces using `Thread.getStackTrace()` and then just does some basic validation of those stacktrace elements. Do we use this `@requires vm.continuations` even in such tests?

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PR: https://git.openjdk.org/jdk/pull/12426