Test Coverage Improver

Use this skill when you need a prioritized, risk-aware plan to improve tests from coverage results.

Usage assumptions

• Focus scope is either changed lines/files, a module, or the whole repository.
• Reuse a supplied coverage artifact when its revision, scope, and format match.
• If required context is missing, call out assumptions explicitly before proposing work.

Workflow

1. Define scope and baseline

   • Derive the revision and scope from the request, diff, or supplied report.
   • Default to the affected files/module; whole-workspace coverage requires that scope in the request. Ask only if a wrong scope would change the result.

2. Obtain coverage evidence

   • First inspect a matching existing artifact; do not regenerate it merely because this skill was selected.
   • If measurement is needed, read the Coverage section of the testing guide, check disk space/tool availability, and select package/test-scoped cargo llvm-cov using the repository's nextest configuration. make coverage measures the whole workspace (excluding E2E) and is only for that requested scope.
   • Collect only metrics the report supports. Missing branch/changed-line coverage is unknown, not zero.
   • If measurement cannot run, continue with code-based test proposals and mark measured coverage unverified; do not invent a coverage percentage.

3. Rank highest-risk gaps

   • Prioritize changed code, branch coverage gaps, and low-confidence boundaries.
   • Apply the risk rubric in coverage-prioritization.md.
   • Report up to 5–8 evidenced gaps; do not pad a small scope.
   • For each gap, capture: file, lines, uncovered branches, and estimated risk score.

4. Propose high-impact tests

   • For each gap, name the behavior and regression, distinguishing assertions, relevant normal/edge/failure cases, necessary setup, and estimated effort.
   • Include only scenarios and setup that apply; reuse shared fixture details.

5. Close with validation plan

   • State which gaps remain after proposals.
   • Give a scoped verification command and behavior-based acceptance criterion; use a coverage threshold only when the task or repository requires one.
   • List assumptions or blockers (environment, fixtures, flaky dependencies).

Report

Summarize the supported metrics, then combine each ranked gap with its proposed test and validation. Include source lines only when supplied or inspected; mark missing metrics or locations as unknown. Do not duplicate gaps and tests in separate templates or fill empty categories for an otherwise small report.