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

• Tests
  • Added extensive unit tests covering edge cases, event/link combinations, encoding consistency, status/flag mappings, and completeness of traced-field handling—improving confidence and reliability of telemetry/trace processing.

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[coderabbitai]

Walkthrough

Added a suite of unit tests to src/otel/traces.rs validating flattening behavior for events, links, and span records, including empty-input edge cases and known-field / encoding consistency checks. No production code or API changes.

Changes

Cohort / File(s)	Summary
Unit tests for OTEL traces flattening src/otel/traces.rs	Added ~13 unit tests covering: empty-event/link slices, event-only and link-only span enrichment, spans with both events and links and without either, hex-encoding consistency, complete flattened-traces structure, and known-field-list completeness. No production logic changes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• update trace field names for events and links #1455: Adds unit tests that directly exercise event/link flattening and known-field handling in src/otel/traces.rs.
• changes to otel data #1446: Related changes to known-field lists and flattening signatures for traces that these tests validate.
• fix: otel traces flattening fix #1196: Introduced or adjusted the flattening logic whose behavior is targeted by these tests.

Suggested reviewers

• nikhilsinhaparseable
• parmesant

Poem

🐇 I nibble at bytes and hop through tests,

Events and links in tidy nests.
Empty slices bowed and checked,
Known fields counted, hex direct.
Hooray — the traces pass the quest!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Title accurately describes the main change: adding unit tests for empty events/links flattening in OTel traces.
Description check	✅ Passed	PR description comprehensively covers the purpose, specific tests added, and their validation targets. However, the description template's testing/documentation checklist items were not addressed.
Linked Issues check	✅ Passed	The PR directly addresses issue #1198 by adding four targeted unit tests that document and validate the expected behavior of the flattening logic introduced in #1196.
Out of Scope Changes check	✅ Passed	All changes are scoped to adding unit tests in src/otel/traces.rs; no production code modifications or unrelated changes are present.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

📝 Coding Plan

• Generate coding plan for human review comments

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[LeC-D]

I have read the CLA Document and I hereby sign the CLA

[nitisht]

Thanks for the PR @LeC-D - looks like the commit email id is not linked to github account, so the CLA Assistant is failing. Would you add your commit email to github, so the CLA is signed properly.

[LeC-D]

I have read the CLA Document and I hereby sign the CLA

[coderabbitai]

🧹 Nitpick comments (2)

src/otel/traces.rs (2)

1059-1114: Well-structured test for events-only span flattening.

The test correctly validates that a span with events but no links produces one record per event, each enriched with span-level fields.

Consider also asserting that link-specific fields are absent from event records for completeness (similar to how test_flatten_span_record_without_events_and_links verifies absence of both):

💡 Optional enhancement

         // Each event record must also carry the span-level fields.
         for record in &result {
             assert_eq!(
                 record.get("span_name").unwrap(),
                 &Value::String("events-only-span".to_string()),
                 "Event records must be enriched with span fields"
             );
+            assert!(
+                !record.contains_key("link_trace_id"),
+                "Event-only records should not contain link fields"
+            );
         }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/otel/traces.rs` around lines 1059 - 1114, Update the test
test_flatten_span_record_events_only_no_links to also assert that link-specific
fields are absent on each event record: after the existing span-level checks,
iterate the result and assert that keys such as "link_trace_id" and
"link_span_id" (and any other link-related keys your flatten_span_record
produces) are either None or not present (e.g.,
record.get("link_trace_id").is_none()). This keeps the test aligned with
flatten_span_record's behavior and mirrors the completeness checks in
test_flatten_span_record_without_events_and_links.

---

1116-1158: Good coverage for links-only span flattening.

The test correctly validates that a span with links but no events produces one record per link, enriched with span-level fields.

For symmetry with the events-only test enhancement, consider also verifying the absence of event-specific fields:

💡 Optional enhancement

         assert_eq!(
             result[0].get("span_name").unwrap(),
             &Value::String("links-only-span".to_string()),
             "Link records must be enriched with span fields"
         );
+        assert!(
+            !result[0].contains_key("event_name"),
+            "Link-only records should not contain event fields"
+        );
     }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/otel/traces.rs` around lines 1116 - 1158, Update the
test_flatten_span_record_links_only_no_events test to also assert that
event-specific fields are not present on link records: after calling
flatten_span_record(&span) and the existing link assertions, add checks that
result[0] does not contain keys such as "event_name", "event_time_unix_nano",
"event_attributes" (or any other event-related keys used by flatten_span_record)
to ensure link-only records aren't populated with event fields.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/otel/traces.rs`:
- Around line 1059-1114: Update the test
test_flatten_span_record_events_only_no_links to also assert that link-specific
fields are absent on each event record: after the existing span-level checks,
iterate the result and assert that keys such as "link_trace_id" and
"link_span_id" (and any other link-related keys your flatten_span_record
produces) are either None or not present (e.g.,
record.get("link_trace_id").is_none()). This keeps the test aligned with
flatten_span_record's behavior and mirrors the completeness checks in
test_flatten_span_record_without_events_and_links.
- Around line 1116-1158: Update the
test_flatten_span_record_links_only_no_events test to also assert that
event-specific fields are not present on link records: after calling
flatten_span_record(&span) and the existing link assertions, add checks that
result[0] does not contain keys such as "event_name", "event_time_unix_nano",
"event_attributes" (or any other event-related keys used by flatten_span_record)
to ensure link-only records aren't populated with event fields.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 6145842c-7f9c-43e1-bf48-c64391473ca0

📥 Commits

Reviewing files that changed from the base of the PR and between ffc3e69 and 7a1b8fd.

📒 Files selected for processing (1)

• src/otel/traces.rs