improve-code-coverage

name	improve-code-coverage
description	Make the current branch satisfy the Glific frontend Codecov gates (project + patch) by finding uncovered changed lines with Vitest/istanbul coverage and adding focused, behavior-asserting tests until green. Use when the user asks to improve coverage, fix a codecov/patch or codecov/project failure, or satisfy codecov.yml on the current branch.
disable-model-invocation	true

Improve Code Coverage (Frontend)

Iterative loop: generate Vitest coverage, find uncovered changed lines, add tests that assert real behavior, repeat until the gate is green. No git push or Codecov upload required to iterate.

Gates (codecov.yml)

Check	Rule
project	target 81.5%, threshold 0.5%
patch	threshold 0% — every changed line in the diff must be covered

The patch gate is strict: a single uncovered new/changed line fails codecov/patch. Most failures are an un-exercised callback (e.g. an onApply/onClose/onError handler) or an error branch.

Tools

• yarn test:coverage — full suite coverage (istanbul). Slow; use for the final check.
• Scoped coverage for a single file (fast iteration):

  CI=true npx vitest run src/path/to/File.test.tsx \
    --coverage --coverage.include='src/path/to/File.tsx'
  

  The report’s Uncovered Line #s column is your worklist.
• Map uncovered lines to your diff (only changed lines count for patch):

  git diff -U0 origin/master -- src/path/to/File.tsx | grep '^@@'
  

  Lines outside your @@ hunks are pre-existing — ignore them for codecov/patch.

Loop (repeat until green)

1. Run scoped coverage on the changed file(s); note Uncovered Line #s.
2. Cross-check against your diff hunks — keep only uncovered lines you added/changed.
3. Add/extend a test that exercises and asserts that line’s behavior:
   • Prefer existing mocks in src/mocks/ and MockedProvider.
   • To cover a callback handler without driving a heavy child’s real async, mock the child so it calls the handler directly (see fix-flaky-tests §6). This avoids real timers and keeps the test fast and deterministic.
   • Cover error branches with the matching error mock (e.g. …ErrorMocks).
4. Re-run scoped coverage; repeat until no changed lines are uncovered.
5. Final: npx tsc --noEmit (0 errors) and npx prettier --check <changed test files>.

Hard rules

• Never weaken codecov.yml, exclude files, or lower thresholds to go green.
• Never add tests that only execute lines without asserting behavior.
• If codecov/patch is failing on lines outside your PR’s scope, stop and ask the user — don’t backfill unrelated coverage.
• Don’t commit unless the user asked; iterate on the working tree.

When to ask the user

• 5 loops without green.
• Patch gaps require large unrelated test work.
• A changed line is genuinely untestable (e.g. defensive default branch) — propose excluding just that line with an istanbul ignore comment and ask before adding it.

Related skills

• fix-flaky-tests — if a test fails intermittently during a coverage run, or you need fake-timers/child-mocking to cover async handlers.
• make-branch-ready-for-review — push + poll CI/Codecov after the local gate is green.