HDDS-9252. NPE in TestNSSummaryTask

[adoroszlai]

What changes were proposed in this pull request?

TestNSSummaryTask and related tests are implemented as nested classes. If we run the nested test class directly (either explictly, or via some selector, e.g. package name), these nested classes run into exceptions, because JUnit does not execute the @BeforeClass setup code in the outer class.

This change converts these tests to JUnit5, which handles nested class setup properly.

https://issues.apache.org/jira/browse/HDDS-9252

How was this patch tested?

$ mvn -am -pl :ozone-recon -Dtest='TestNSSummaryTaskWithLegacy$TestProcess' clean test
...
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTaskWithLegacy
[INFO] Running org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTaskWithLegacy$TestProcess
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.055 s - in org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTaskWithLegacy$TestProcess
[INFO] Tests run: 0, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.768 s - in org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTaskWithLegacy
...

$ mvn -am -pl :ozone-recon -Dtest='TestNSSummaryTask$TestReprocess' clean test
[INFO] Running org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTask
[INFO] Running org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTask$TestReprocess
[INFO] Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.04 s - in org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTask$TestReprocess
[INFO] Tests run: 0, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.876 s - in org.apache.hadoop.ozone.recon.tasks.TestNSSummaryTask
...

CI:
https://github.com/adoroszlai/hadoop-ozone/actions/runs/6163907068/job/16728478679

[adoroszlai]

@ArafatKhan2198 alternative fix for HDDS-9252, keeping nested test structure

[hemantk-12]

LGTM +1

[adoroszlai]

Thanks @hemantk-12 for the review.