← Docs
Recipe

Test coverage gap finder

Identify untested code paths by diffing production traces against your test suite. Ship with confidence.

Ingredients

  • Production trace logs (JSON Lines, one span per line)
  • Test suite coverage report (LCOV or Cobertura XML)
  • Meridian agent running on staging

Steps

  1. Collect production traces. Run meridian trace --env prod --duration 1h and pipe to a file.
  2. Generate test coverage. Run your test suite with coverage enabled. Export as LCOV.
  3. Run the gap analyzer. Feed both files into the Meridian CLI:
    meridian gap --traces prod.jsonl --coverage coverage.lcov
  4. Review the report. The tool emits a ranked list of uncovered functions hit in production, sorted by call frequency.
  5. Write the missing tests. Prioritize high-frequency gaps first.

Output

A Markdown report listing each uncovered function, its file path, line range, and production hit count. Example:

## Coverage Gaps
| Function | File | Lines | Prod Hits |
|----------|------|-------|-----------|
| validateSession | auth/session.ts | 42-58 | 12,401 |
| parseWebhook | webhooks/ingest.ts | 101-119 | 8,203 |

Notes

  • Requires Meridian agent v2.4+ with tracing enabled.
  • Works with any language — traces and coverage are format-agnostic.
  • Run weekly to catch regressions as code evolves.

Need help wiring this into CI? Read the CI integration guide →