Fix flaky test in MetadataIndexTemplateServiceTests

[liuguoqingfz]

Description

Fix a flaky test where there is a test expectation mismatch.
the test asserts that the thrown InvalidIndexTemplateException message contains:
"specifies a context which cannot be used without enabling"
But the current code path throws a different message:
"specifies a context which is not loaded on the cluster."
It typically happens when the validation order changed or a different validation branch triggers first instead of “context feature disabled”, it now fails earlier/later with “context not loaded”.

Related Issues

Resolves #19058

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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Summary by CodeRabbit

• Tests
  • Enhanced exception message validation in metadata index template tests for improved assertion accuracy.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

The changes refactor two test assertions in MetadataIndexTemplateServiceTests to store exception messages in local variables and use them in assertions instead of making repeated calls to ex.getMessage(). This improves assertion clarity and addresses flaky test behavior by ensuring consistent message validation.

Changes

Cohort / File(s)	Change Summary
Test assertion refactoring server/src/test/java/org/opensearch/cluster/metadata/MetadataIndexTemplateServiceTests.java	Introduced local msg variable to store exception messages in two test methods; updated assertions to use the variable instead of repeated ex.getMessage() calls; first assertion validates both "specifies a context which cannot be used without enabling" and "specifies a context which is not loaded on the cluster" conditions.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Suggested labels

flaky-test

Suggested reviewers

• sachinpkale
• saratvemulapalli
• andrross
• dbwiddis
• cwperks
• msfroh

Poem

🐰 With messages now caught and held tight,
No flaky assertions to cause a fright,
A local variable brings clarity clear,
The tests shall be steady, the results sincere!

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description provides context on the test flakiness, explains the root cause (expectation mismatch between two possible exception messages), and references the related issue #19058. All key sections are present.
Linked Issues check	✅ Passed	The PR addresses the flaky test failure in testPutGlobalV2TemplateWhichProvidesContextWithContextDisabled by updating assertions to accept both possible exception messages, directly resolving the objective stated in linked issue #19058.
Out of Scope Changes check	✅ Passed	All changes are limited to updating test assertions in MetadataIndexTemplateServiceTests.java to handle both possible exception messages, which is directly in scope for fixing the flaky test reported in issue #19058.
Title check	✅ Passed	The title 'Fix flaky test in MetadataIndexTemplateServiceTests' directly and clearly describes the main change - fixing a flaky test in the specific test file modified in the changeset.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[cwperks]

Wouldn't this be the wrong assertion for testPutGlobalV2TemplateWhichProvidesContextWithContextDisabled? I think it would be better to understand why this is being thrown to prevent it.

[cwperks]

Maybe the failing test needs to be annotated with @LockFeatureFlag(APPLICATION_BASED_CONFIGURATION_TEMPLATES)?

[github-actions]

❌ Gradle check result for cacc32a: null

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?