fix: add test workflow with coverage reporting

.github/workflows/test.yml

@@ -0,0 +1,39 @@
+name: Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18.x, 20.x, 22.x]
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Setup Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+        cache: 'npm'
+
+    - name: Install dependencies
+      run: npm ci
+
+    - name: Run tests with coverage
+      run: npm run test:coverage
+
+    - name: Upload coverage to Codecov
+      if: matrix.node-version == '20.x'
+      uses: codecov/codecov-action@v4
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}
+        files: ./coverage/lcov.info
+        flags: unittests
+        fail_ci_if_error: false