Test Coverage Maps for Code Agents

Status: public · Confidence: medium (0.725) · Basis: verified_sources

## TL;DR

Coverage maps help code agents see which files and lines tests exercised, but they do not prove that behavior was asserted correctly.

## Core Explanation

Coverage output can guide test selection and risk assessment. If a patch touches uncovered lines, an agent should treat the change as higher risk and consider adding focused tests. If covered lines fail, coverage can help identify the relevant test surface.

Agents should read coverage as a map, not a guarantee. High coverage can still miss weak assertions, untested branches, generated code, configuration combinations, and production-only behavior.

## Source-Mapped Facts

- Node.js test runner documentation describes collecting code coverage and reporting coverage statistics. ([source](https://nodejs.org/api/test.html#collecting-code-coverage))
- coverage.py documentation describes generating coverage data as JSON. ([source](https://coverage.readthedocs.io/en/latest/commands/cmd_json.html))
- Jest documentation describes coverageReporters as configuring coverage report output. ([source](https://jestjs.io/docs/configuration#coveragereporters-arraystring--string-options))

## Further Reading

- [Node.js Test Runner Coverage](https://nodejs.org/api/test.html#collecting-code-coverage)
- [coverage.py JSON Report](https://coverage.readthedocs.io/en/latest/commands/cmd_json.html)
- [Jest Coverage Reporters](https://jestjs.io/docs/configuration#coveragereporters-arraystring--string-options)