dart-collect-coverage

Contents

• Setup
• Automated Collection
• Flutter-Specific Coverage
• Manual VM Service Workflow
• Coverage Ignore Directives
• CI Integration
• Workflow: Generating Coverage Reports
• Examples

Setup

Add coverage strictly as a dev_dependency:

Dart project:

dart pub add dev:coverage

Flutter project:

flutter pub add dev:coverage

Automated Collection

Use the bundled test_with_coverage script for one-command coverage:

dart run coverage:test_with_coverage

This automatically:

1. Runs all tests
2. Collects JSON coverage from the Dart VM
3. Formats into LCOV report at coverage/lcov.info

Monorepo support: specify test directories explicitly:

dart run coverage:test_with_coverage -- pkgs/foo/test pkgs/bar/test

Flutter-Specific Coverage

Generate LCOV

flutter test --coverage

Outputs coverage/lcov.info at project root.

Generate HTML Report

# Install lcov (macOS)
brew install lcov

# Generate HTML from LCOV
genhtml coverage/lcov.info -o coverage/html

# Open in browser
open coverage/html/index.html

Filter Out Generated Code

lcov --remove coverage/lcov.info \
  '*.g.dart' \
  '*.freezed.dart' \
  '*.part.dart' \
  -o coverage/lcov_cleaned.info

Manual VM Service Workflow

For granular control over coverage collection (branch/function-level):

1. Run Tests with VM Service

dart run --pause-isolates-on-exit \
  --disable-service-auth-codes \
  --enable-vm-service=8181 \
  test &

2. Collect Raw Coverage

dart run coverage:collect_coverage \
  --wait-paused \
  --uri=http://127.0.0.1:8181/ \
  -o coverage/coverage.json \
  --resume-isolates \
  --function-coverage \
  --branch-coverage

Optional flags:

• --function-coverage: function-level metrics (Dart VM 2.17.0+)
• --branch-coverage: branch-level metrics (Dart VM 2.17.0+)

3. Format to LCOV

dart run coverage:format_coverage \
  --packages=.dart_tool/package_config.json \
  --lcov \
  -i coverage/coverage.json \
  -o coverage/lcov.info \
  --check-ignore

Coverage Ignore Directives

Exclude specific code from coverage metrics using inline comments. Pass --check-ignore during formatting to enforce.

Directive	Scope	Usage
// coverage:ignore-line	Single line	Unreachable branches, platform checks
// coverage:ignore-start / // coverage:ignore-end	Block	Generated code, legacy methods
// coverage:ignore-file	Entire file	Generated files, config files

// coverage:ignore-file
// This entire file is excluded from coverage

class GeneratedRoutes {
  // coverage:ignore-start
  void legacyInit() {
    print('Deprecated initialization');
  }
  // coverage:ignore-end

  bool isProduction(String env) {
    if (env == 'prod') return true;
    return false; // coverage:ignore-line
  }
}

CI Integration

GitHub Actions Coverage Gate

- name: Run tests with coverage
  run: flutter test --coverage

- name: Check coverage threshold
  run: |
    COVERAGE=$(lcov --summary coverage/lcov.info 2>&1 | grep "lines" | awk '{print $2}' | sed 's/%//')
    echo "Coverage: $COVERAGE%"
    if (( $(echo "$COVERAGE < 80" | bc -l) )); then
      echo "Coverage below 80% threshold!"
      exit 1
    fi

- name: Upload coverage
  uses: codecov/codecov-action@v4
  with:
    files: coverage/lcov.info

Coverage Targets (from AGENTS.md)

• 100% logic coverage for domain and bloc layers.
• Widget coverage for all major UI components.
• Use // coverage:ignore-file for generated code (.g.dart, .freezed.dart).

Workflow: Generating Coverage Reports

Task Progress

• Step 1: Add coverage to dev_dependencies.
• Step 2: Run flutter test --coverage (or dart run coverage:test_with_coverage).
• Step 3: Validate coverage/lcov.info exists.
• Step 4: Filter generated code: lcov --remove ... '*.g.dart' '*.freezed.dart'.
• Step 5: Generate HTML: genhtml coverage/lcov.info -o coverage/html.
• Step 6: Review uncovered files: add tests or // coverage:ignore-file.
• Step 7: Add coverage gate to CI pipeline (80% minimum).

Examples

pubspec.yaml Configuration

name: my_app
environment:
  sdk: ^3.0.0

dev_dependencies:
  flutter_test:
    sdk: flutter
  coverage: ^1.15.0
  bloc_test: ^9.1.0
  mocktail: ^1.0.0

Quick Coverage Check Script

#!/bin/bash
# scripts/coverage.sh
set -e

echo "Running tests with coverage..."
flutter test --coverage

echo "Filtering generated code..."
lcov --remove coverage/lcov.info \
  '*.g.dart' '*.freezed.dart' '*.part.dart' \
  -o coverage/lcov_cleaned.info

echo "Generating HTML report..."
genhtml coverage/lcov_cleaned.info -o coverage/html

echo "Opening report..."
open coverage/html/index.html