Expand src/lib/heartbeat.test.ts to cover aggregation, touchedIssueUrls, and warning/error bucketing

[itsmiso-ai]

Parent umbrella issue: #408
Source audit: Weekly tech debt audit: dispatch - 2026-06-17
Source audit date: 2026-06-17

Original recommendation

P3 — Expand src/lib/heartbeat.test.ts to cover aggregation, touchedIssueUrls, and warning/error bucketing.

Matched top finding

src/lib/heartbeat.test.ts is 82 lines and only covers the runSyncBestEffort / runReconcileBestEffort happy/empty paths. The 184-line heartbeat.ts includes aggregation, touchedIssueUrls collection, and warning/error bucket logic that is not covered. The integration is covered by src/app/api/agents/[agentName]/heartbeat/route.test.ts (412 lines) but the unit-level coverage is thin.

Evidence:

• wc -l src/lib/heartbeat.ts src/lib/heartbeat.test.ts → 184 vs 82.
• grep -c "describe\|it(" src/lib/heartbeat.test.ts → 2.