Fix flaky test in 91_flat_object_null_value.yml

[msfroh]

Description

This test assumed that the order of returned hits will match the order of insertion. That's not generally true, especially if there was a flush partway through, so documents end up in different segments.

This fixes it by explicitly sorting the returned documents to guarantee that they come back in the correct order.

Also, we were getting a NPE when trying to output the failure message because the expected value was intentionally null. I fixed that too.

Related Issues

N/A (I don't believe we have a flaky-test issue for this one. Thanks @mch2 for bringing it to my attention!)

Check List

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

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[github-actions]

❌ Gradle check result for 8fecdc5: FAILURE

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?

[github-actions]

❌ Gradle check result for 99ff88d: FAILURE

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?

[github-actions]

❌ Gradle check result for 99ff88d: FAILURE

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?

[github-actions]

❌ Gradle check result for 99ff88d: FAILURE

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?

[github-actions]

❌ Gradle check result for 99ff88d: FAILURE

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?

[github-actions]

❌ Gradle check result for 8c187d5: FAILURE

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?

[msfroh]

❌ Gradle check result for 8c187d5: FAILURE

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?

Oops -- This one is me. I added the new order field, but there was a test checking that the mapping only contained 1 field.

[github-actions]

❕ Gradle check result for ba7a34a: UNSTABLE

• TEST FAILURES:

      1 org.opensearch.backwards.MixedClusterClientYamlTestSuiteIT.test {p0=snapshot.status/10_basic/Get missing snapshot status throws an exception}

Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.83%. Comparing base (3fc0139) to head (ba7a34a).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #15545      +/-   ##
============================================
- Coverage     71.97%   71.83%   -0.15%     
+ Complexity    64067    63977      -90     
============================================
  Files          5259     5259              
  Lines        299431   299431              
  Branches      43270    43270              
============================================
- Hits         215527   215105     -422     
- Misses        66217    66672     +455     
+ Partials      17687    17654      -33     

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