nightly-add-test-coverage

name	nightly-add-test-coverage
description	Nightly direct-execution skill for increasing test coverage. Receives pre-computed threshold data, writes tests targeting coverage gaps, updates thresholds, commits, and creates a PR.
allowed-tools	["Edit","MultiEdit","Write","Read","Glob","Grep","Bash"]

Nightly Test Coverage Improvement

The caller provides pre-computed context:

• Package manager (npm, yarn, or bun)
• Thresholds file path (vitest.thresholds.json or jest.thresholds.json)
• Current thresholds (statements, branches, functions, lines percentages)
• Proposed thresholds (each metric increased by the coverage increment, capped at 90%)
• Metrics being bumped (which metrics are below target)

Instructions

Phase 1: Identify gaps

1. Run the project's coverage script with the provided package manager (e.g., npm run test:cov, yarn test:cov, or bun run test:cov) to get the coverage report -- identify gaps BEFORE reading any source files
2. Parse the coverage output to identify the specific files and lines with the lowest coverage. Prioritize files with the most uncovered lines/branches.
3. Read ONE existing test file to learn the project's testing patterns (mocks, imports, assertions). Do not read more than one.

Phase 2: Write tests incrementally — one file at a time

For each source file with low coverage (starting with the lowest):

4. Read only the uncovered sections of the source file using the coverage report line numbers -- do not explore the codebase broadly
5. Write a test file targeting the uncovered branches/lines for that source file
6. Run the test file in isolation (e.g., npx vitest run tests/my-new-test.test.ts) to verify it passes before moving on
7. If the test fails, fix it immediately. Do not move to the next file until the current test passes.
8. Repeat steps 4-7 for the next source file. Stop once you estimate the proposed thresholds will be met.

Phase 3: Verify and ship

9. Run the full coverage script to verify the new thresholds pass
10. Update the thresholds file with the proposed new threshold values
11. Re-run the coverage script to confirm the updated thresholds pass
12. Commit all changes (new tests + updated thresholds file) with conventional commit messages
13. Create a PR with gh pr create with a title like "test: increase test coverage: [metrics being bumped]" summarizing coverage improvements