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In this guide, we’ll enhance an existing GitHub Actions workflow by adding a dedicated code coverage job. The new job runs in parallel with unit tests, generates coverage reports using npm run coverage, and archives the results for later inspection.

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Environment Variables

Make sure the following variables are defined in your repository settings:
VariablePurpose
MONGO_URIMongoDB connection URI
MONGO_USERNAMEMongoDB username (GitHub Variable)
MONGO_PASSWORDMongoDB password (GitHub Secret)

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1. Existing Unit Testing Job

This YAML snippet configures a matrix-based unit testing job across multiple Node.js versions and OS environments: 
env:
  MONGO_URI: 'mongodb+srv://supercluster.d83jj.mongodb.net/superData'
  MONGO_USERNAME: ${{ vars.MONGO_USERNAME }}
  MONGO_PASSWORD: ${{ secrets.MONGO_PASSWORD }}

jobs:
  unit-testing:
    name: Unit Testing
    strategy:
      matrix:
        nodejs_version: [18, 19, 20]
        operating_system: [ubuntu-latest, macos-latest]
      exclude:
        - nodejs_version: 18
          operating_system: macos-latest
    runs-on: ${{ matrix.operating_system }}
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v4

      - name: Setup Node.js ${{ matrix.nodejs_version }}
        uses: actions/setup-node@v3
        with:
          node-version: ${{ matrix.nodejs_version }}

      - name: Install Dependencies
        run: npm install

      - name: Run Unit Tests
        run: npm test

      - name: Archive Test Results
        uses: actions/upload-artifact@v3
        with:
          name: Unit-Test-Results
          path: test-results
          retention-days: 5

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2. Job Overview

JobRuns OnScript
unit-testingMatrix: Node.js 18/19/20 on Ubuntu/MacOSnpm test
code-coverageUbuntu-latest, Node.js 18npm run coverage

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3. Adding the Code Coverage Job

Add a second job named code-coverage right below the existing unit-testing definition: 
env:
  MONGO_URI: 'mongodb+srv://supercluster.d83jj.mongodb.net/superData'
  MONGO_USERNAME: ${{ vars.MONGO_USERNAME }}
  MONGO_PASSWORD: ${{ secrets.MONGO_PASSWORD }}

jobs:
  unit-testing: # existing job…

  code-coverage:
    name: Code Coverage
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Repository
        uses: actions/checkout@v4

      - name: Setup Node.js 18
        uses: actions/setup-node@v3
        with:
          node-version: 18

      - name: Install Dependencies
        run: npm install

      - name: Generate Coverage Report
        run: npm run coverage

      - name: Archive Coverage Report
        uses: actions/upload-artifact@v3
        with:
          name: Code-Coverage-Result
          path: coverage
          retention-days: 5
Running npm run coverage outputs coverage data under the coverage folder, which the upload-artifact action then archives for 5 days.

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4. Viewing Artifacts in the GitHub Actions UI

Artifacts from each workflow run appear in the Artifacts section of the run summary. You can remove individual artifacts manually or rely on the retention-days setting for automatic cleanup.
The image shows a GitHub Actions page for a repository named "solar-system," displaying a list of workflow runs with their statuses and details.

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5. Handling Coverage Threshold Failures

If your global coverage threshold (for example, 90%) isn’t met, the coverage step exits with a non-zero code. Subsequent steps—including artifact uploads—are skipped.
ERROR: Coverage for lines (88.88%) does not meet global threshold (90%)
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-----------|---------|----------|---------|---------|-------------------
All files  |   88.88 |      50  |   87.5  |   88.88 | 21, 47-48, 56
app.js     |   88.88 |      50  |   87.5  |   88.88 | 21, 47-48, 56
Error: Process completed with exit code 1.
The image shows a GitHub Actions workflow summary for a project named "solar-system," where unit tests have passed, but the code coverage job has failed. The status is marked as "Failure" with a total duration of 58 seconds.
The image shows a GitHub Actions workflow interface with a list of jobs, where "Code Coverage" has failed, while several unit testing jobs have succeeded.
To ensure artifact upload even on failure, consider using continue-on-error: true for the coverage step or placing the upload step in a separate always() conditional.

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6. Next Steps

  • Write additional tests to boost coverage above your threshold.
  • Tweak or disable the coverage threshold in your test config.
  • Implement error-handling strategies to archive critical artifacts regardless of step failures.

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