test(otel): add unit tests for empty events/links flattening (#1198)

[LeC-D]

Summary

Closes #1198

What

Adds four targeted unit tests to src/otel/traces.rs that document the expected behaviour of the specialised flattening logic introduced in #1196 (empty Events / Links in OTel spans):

Test	What it validates
test_flatten_events_empty_slice	flatten_events(&[]) returns an empty Vec
test_flatten_links_empty_slice	flatten_links(&[]) returns an empty Vec
test_flatten_span_record_events_only_no_links	Span with 2 events, 0 links → 2 records each enriched with span fields
test_flatten_span_record_links_only_no_events	Span with 0 events, 1 link → 1 record enriched with span fields

The if span_records_json.is_empty() branch in flatten_span_record is the critical path for the #1196 fix; these tests pin its contract so that any future refactor that breaks the fallback will be caught immediately.

Summary by CodeRabbit

Release Notes

• Tests
  • Enhanced test coverage with new unit tests validating edge cases and data enrichment behavior in telemetry processing, ensuring improved reliability of trace handling.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: ad6d2355-b88d-4f30-bed9-ab8e7b9df605

📥 Commits

Reviewing files that changed from the base of the PR and between fd9b9a4 and ffc3e69.

📒 Files selected for processing (1)

• src/otel/traces.rs

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Walkthrough

Unit tests were added to validate the behavior of event and link flattening functions in the OpenTelemetry traces module. Tests cover empty input edge cases and verify that enriched span fields are correctly included in flattened records for both events and links.

Changes

Cohort / File(s)	Summary
Unit Tests for Flattening Logic src/otel/traces.rs	Added four unit tests: test_flatten_events_empty_slice, test_flatten_links_empty_slice, test_flatten_span_record_events_only_no_links, and test_flatten_span_record_links_only_no_events to validate empty-input handling and per-event/per-link enrichment behavior.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• fix: otel traces flattening fix #1196: Introduced the flattening logic and behavior that these tests validate.
• fix: stringify otel attributes of array types #1298: Modified the function signatures and attribute-handling logic for the same flattening functions being tested.
• test: add comprehensive unit tests for OTEL traces flattening functionality. #1342: Adds overlapping unit test coverage for the same flattening functions in src/otel/traces.rs.

Suggested reviewers

• nikhilsinhaparseable
• parmesant

Poem

🐰 With whiskers twitching, tests now hop,
Empty slices? They never stop!
Events and links in flattened grace,
Each test finds its perfect place! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding unit tests for empty events/links flattening in the OTel module, with reference to the related issue.
Description check	✅ Passed	The description is well-structured with a clear summary table showing what each test validates, explaining the rationale for pinning the critical path contract.
Linked Issues check	✅ Passed	The PR directly addresses issue #1198 by adding four unit tests that document and validate the behavior of specialized flattening code for empty events/links, fulfilling the objective to document expected contract.
Out of Scope Changes check	✅ Passed	All changes are within scope: only unit tests added to src/otel/traces.rs with no modifications to existing implementations or APIs, directly aligned with #1198 requirements.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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