[fix][test] Fix flaky PulsarFunctionsJavaThreadTest.testTumblingCountWindowTest

[Praveenkumar76]

Fixes apache#25391

Motivation

PulsarFunctionsJavaThreadTest.testTumblingCountWindowTest fails intermittently in CI with assertion errors such as:

expected [1] but found [3]

The failure is caused by race conditions in the test. It validates TopicStats and SubscriptionStats immediately after producing messages, while broker statistics are updated asynchronously. As a result, the test may read stale or partially updated values.

Additionally, some assertions use inverted parameter ordering, which makes failure messages harder to interpret.

Modifications

• Replaced immediate metric assertions with Awaitility.await().untilAsserted(...) so the test waits until broker stats reach the expected values.
• Applied asynchronous waiting for both backlog verification and final acknowledgment / cleanup checks.
• Corrected assertEquals argument ordering to improve assertion readability and failure diagnostics.
• Improved test stability by aligning assertions with the eventual consistency behavior of broker metrics.

Verifying this change

This change is a bug fix and was verified manually:

• Re-ran PulsarFunctionsJavaThreadTest.testTumblingCountWindowTest multiple times locally without intermittent failures.
• Confirmed the test now waits for expected metrics before asserting.
• Executed the targeted Gradle integration test successfully:

./gradlew :tests:integration:test --tests "*PulsarFunctionsJavaThreadTest.testTumblingCountWindowTest"

Starting a Gradle Daemon (subsequent builds will be faster)
Configuration on demand is an incubating feature.
Reusing configuration cache.

BUILD SUCCESSFUL in 2s
98 actionable tasks: 5 executed, 1 from cache, 92 up-to-date

• CI validation pending / to be confirmed after PR run.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

[lhotari]

minor details in using Awaitility

[Praveenkumar76]

@lhotari ! I've removed the redundant Awaitility defaults as suggested and ensured the CI checks are passing

[lhotari]

LGTM, thanks for the contribution @Praveenkumar76