test(showcase): add IT against showcase for ResumableUploadCallable

[whowes]

For illustration only - this PR will not be merged. This is basically a unit test for the Callable except against the showcase fake rather than mocks. The proper IT for resumable uploads will operate on the client library level rather than the Callable.

[gemini-code-assist]

Code Review

This pull request adds a new integration test class, ITResumableUploadCallable, to verify the resumable upload pipeline against Showcase under various scenarios, including single-chunk, multi-chunk, zero-byte uploads, timeouts, and cancellations. The review feedback recommends awaiting the termination of the ScheduledExecutorService during teardown to prevent potential thread leaks.

[gemini-code-assist]

The ScheduledExecutorService is shut down using shutdownNow(), but its termination is not awaited. To prevent thread leaks and ensure resources are fully released before subsequent tests run, please await the executor's termination. Additionally, ensure that teardown or close methods perform explicit null checks before invoking methods on lazily initialized resources to prevent NullPointerException.

    if (executor != null) {
      executor.shutdownNow();
      executor.awaitTermination(TestClientInitializer.AWAIT_TERMINATION_SECONDS, TimeUnit.SECONDS);
    }

References

1. When using lazily initialized resources (such as ExecutorService), ensure that teardown or close methods perform explicit null checks before invoking methods on them to prevent NullPointerException.

[sonarqubecloud]

Quality Gate passed for 'gapic-generator-java-root'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed for 'gapic-generator-java-root'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[blakeli0]

Really like the idea of testing against showcase with callables directly. Never did it before but we should definitely try it more often in the future. Especially with the help of AI, the cost of writing these tests are almost none.