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selamy-labsselamy-labs/agent-skills/skills/feature-coverage-not-just-line-coverage/SKILL.md

feature-coverage-not-just-line-coverage

Skill0 starsChanged 5 days agoMITView on GitHub

Use when coverage percentage is treated as proof. Require named feature behavior tests, source fixtures, and anti-overfit checks alongside line coverage.

The file

We split this skill into the rules it gives an agent

4 rules. About 0 are common, 4 are distinctive, and 0 are very specific to this project.

  • ≈0

    Common · estimate

    Many files like this have a rule of this kind.

  • ≈4

    Distinctive · estimate

    This author's own choices. Worth a look.

  • 0

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Distinctive:

    Use this skill when a change claims safety from line coverage alone or when a feature has no test that names the behavior users depend on.

    line 8
  2. Distinctive:

    Add at least one test, fixture, or acceptance check that proves that promise directly.

    line 14
  3. Distinctive:

    Keep line, branch, or mutation coverage as a floor for untested code paths.

    line 16
  4. Distinctive:

    When fixing a bug, add the cheapest durable guard that would have caught it: unit test for code logic, fixture for parser or data behavior, …

    line 32

≈ “Common” is an estimate: at least 1 in 5 of the 350,495 skill files we read have a rule of the same kind, not the same words. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

Feature Coverage Not Just Line Coverage

Use this skill when a change claims safety from line coverage alone or when a feature has no test that names the behavior users depend on.

Workflow

  1. Name the feature promise in user or system terms.
  2. Add at least one test, fixture, or acceptance check that proves that promise directly.
  3. Keep line, branch, or mutation coverage as a floor for untested code paths.
  4. For generated, ranked, or data-derived behavior, record source lineage and check for leakage, lookahead, copied answers, and overfit fixtures.
  5. Make the CI gate fail when either the coverage threshold or the named feature check fails.

Review Checks

  • The test name or fixture clearly maps to the feature promise.
  • The assertion checks the real output or contract, not only an implementation detail.
  • Fixtures are realistic enough to catch regressions and small enough to review.
  • A high line-coverage number is not used to excuse missing behavior coverage.

Ratchet Pattern

When fixing a bug, add the cheapest durable guard that would have caught it: unit test for code logic, fixture for parser or data behavior, integration test for cross-module contracts, or monitor for an operational failure that tests cannot reproduce.

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