Fix errors when a grouped table is shown

.github/workflows/playwright.yml

@@ -0,0 +1,32 @@
+name: Playwright Tests
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+jobs:
+  test:
+    timeout-minutes: 60
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18, 20, 22]
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+    - name: Install dependencies
+      run: npm ci
+    - name: Install Playwright Browsers
+      run: npx playwright install --with-deps
+    - name: Build dist files
+      run: npm run build
+    - name: Run Playwright tests
+      run: npx playwright test
+    - uses: actions/upload-artifact@v4
+      if: ${{ !cancelled() }}
+      with:
+        name: playwright-report-node-${{ matrix.node-version }}
+        path: playwright-report/
+        retention-days: 30

.github/workflows/unit-tests.yml

@@ -0,0 +1,22 @@
+name: Unit Tests
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        node-version: [18, 20, 22]
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Node.js ${{ matrix.node-version }}
+      uses: actions/setup-node@v4
+      with:
+        node-version: ${{ matrix.node-version }}
+    - name: Install modules
+      run: npm install
+    - name: Run tests
+      run: npm run test:unit

.gitignore

@@ -3,4 +3,10 @@
 
 node_modules/
 examples/
-npm-debug.log
+npm-debug.log
+
+# Playwright
+/test-results/
+/playwright-report/
+/blob-report/
+/playwright/.cache/

README.md

@@ -74,3 +74,22 @@ To access Tabulator directly from the UNPKG CDN servers, include the following t
 <link href="https://unpkg.com/tabulator-tables/dist/css/tabulator.min.css" rel="stylesheet">
 <script type="text/javascript" src="https://unpkg.com/tabulator-tables/dist/js/tabulator.min.js"></script>
 ```
+
+Testing
+================================
+Tabulator comes with both Unit and End-to-End (E2E) tests. Here’s how you can run them:
+
+```bash
+# Unit test
+npm run test:unit
+
+# E2E test
+npm run build # Make sure to build the project first
+npx playwright test # Run the tests
+# or
+npm run test:e2e
+
+# Run all tests
+npm run test
+```
+

babel.config.js

@@ -0,0 +1,11 @@
+module.exports = (api) => {
+    if (api.env("test")) {
+        return {
+            presets: [["@babel/preset-env", { targets: { node: "current" } }]],
+        };
+    }
+
+    return {
+        presets: [["@babel/env", { modules: false }]],
+    };
+};