mobile-test-coverage.mdc

---
description: Flag untested components and screens, missing test files for new code, and low coverage thresholds in React Native/Expo and Flutter projects.
alwaysApply: false
globs:
  - "**/*.ts"
  - "**/*.tsx"
  - "**/*.dart"
standards-version: 1.9.0
---

# Test Coverage

Flag these test coverage issues:

## Missing test files

- A component or screen file (`*.tsx` or `*.dart`) has no corresponding test file (`*.test.tsx`, `*.test.ts`, or `*_test.dart`) in `__tests__/` or a colocated location.
- A utility or hook file has no matching test file.
- New files added in a PR have zero test coverage.

**Fix:** Create a test file using `mobile_generateTestFile` or write tests manually. At minimum, verify the component renders and key interactions work.

## Low coverage thresholds

- Jest `coverageThreshold` in `package.json` is missing or set below 60% for statements.
- Flutter project has no coverage enforcement in CI.

**Fix (Expo):** Add to `package.json`:

```json
{
  "jest": {
    "coverageThreshold": {
      "global": {
        "statements": 60,
        "branches": 50,
        "functions": 60,
        "lines": 60
      }
    }
  }
}
```

**Fix (Flutter):** Add a coverage check step in CI:

```yaml
- run: flutter test --coverage
- name: Check coverage
  run: |
    COVERAGE=$(lcov --summary coverage/lcov.info 2>&1 | grep 'lines' | grep -o '[0-9.]*%' | head -1)
    echo "Line coverage: $COVERAGE"
```

## Snapshot-only testing

- A test file contains only snapshot tests with no behavioral assertions. Snapshot-only tests provide weak coverage and break on any render change.

**Fix:** Add at least one behavioral test per component (user interaction, prop variation, or error state).

## Untested error paths

- Components with `try/catch`, error boundaries, or fallback UI have no tests for the error state.

**Fix:** Write tests that trigger the error path and verify the fallback UI renders.