test: Massive parallel test expansion - 40.72% coverage achieved

Parallel agents completed comprehensive testing:

COMPLETED (Agent a066f29):
✓ Storage/Settings Hooks: 3 files, 48 tests, 100% coverage
  - useStorageConfig.test.ts: 19 tests, 100% statements
  - useStorageMigration.test.ts: 15 tests, 100% coverage
  - useSettingsState.test.ts: 14 tests, 100% coverage
  - Comprehensive mocking of db and storage modules
  - Full async operation coverage
  - Error handling and edge cases

COMPLETED (Agent a190350):
✓ Python Runner Components: 5 files, 201 tests, 98.68% statements
  - PythonTerminal.test.tsx: 29 tests, 100% coverage
  - TerminalHeader.test.tsx: 37 tests, 100% coverage
  - TerminalInput.test.tsx: 38 tests, 100% coverage
  - TerminalOutput.test.tsx: 41 tests, 100% coverage
  - PythonOutput.test.tsx: 56 tests, 97.61% statements
  - Terminal I/O testing, user interactions, error states
  - Accessibility testing (aria-labels, semantic HTML)

COMPLETED (Agent a8af615):
✓ UI Components: 4 files, 94 tests, 99.81% avg coverage
  - tabs.test.tsx: 17 tests, 100% coverage (+61.1%)
  - accordion.test.tsx: 18 tests, 99.25% coverage (+74.65%)
  - dialog.test.tsx: 24 tests, 100% coverage (+77.5%)
  - slider.test.tsx: 35 tests, 100% coverage (+69.4%)
  - Component props, user interactions, accessibility
  - Keyboard navigation, state management, edge cases

IN PROGRESS (Agent a5e3d23):
- Snippet Editor/Viewer: 6-7 files, working through test refinements
- SnippetDialog, SplitScreenEditor, MonacoEditor, SnippetViewer, etc.

OVERALL RESULTS:
- Test Suites: 68 passed, 3 failing (snippet-viewer timing issues)
- Tests: 1,194 passing, 19 failing (being fixed), 1 skipped
- Coverage: 40.72% (up from 29.9%, +10.82 percentage points!)
- Total new tests: 343+ (from 633 → 1,194 tests)
- New test files: 19 files created

KEY ACHIEVEMENTS:
- Parallel agents completed 3 of 4 tasks perfectly
- Generated 1,428 lines of tests for hooks alone
- Achieved 98%+ coverage on Python runner components
- Improved UI components from 22-38% to 99%+ coverage
- All mocking strategies working well (jest.mock, renderHook)
- Zero production code changes needed

COVERAGE IMPROVEMENTS BY COMPONENT:
- Python runner: 0% → 98.68% ✓
- Tabs: 38.9% → 100% ✓
- Accordion: 24.6% → 99.25% ✓
- Dialog: 22.5% → 100% ✓
- Slider: 30.6% → 100% ✓
- Storage hooks: 0% → 100% ✓

Next: Finalize snippet editor/viewer tests (agent still working)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.github/workflows/e2e-tests.yml

@@ -0,0 +1,197 @@
+name: E2E Tests - Batched
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  # Batch 1: Core Functionality & Components (~5-7 min)
+  e2e-batch-1:
+    name: E2E - Functionality & Components
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Install Playwright
+        run: npx playwright install --with-deps
+
+      - name: Run E2E tests - Batch 1
+        run: npx playwright test --grep "Functionality Tests - Core Features|Component-Specific Tests"
+
+      - name: Upload blob report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: blob-report-batch-1
+          path: blob-report
+          retention-days: 30
+
+  # Batch 2: Responsive & Mobile (~8-10 min)
+  e2e-batch-2:
+    name: E2E - Responsive & Mobile
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Install Playwright
+        run: npx playwright install --with-deps
+
+      - name: Run E2E tests - Batch 2
+        run: npx playwright test --grep "Mobile and Responsive Tests"
+
+      - name: Upload blob report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: blob-report-batch-2
+          path: blob-report
+          retention-days: 30
+
+  # Batch 3: Visual & Styling (~10-12 min)
+  e2e-batch-3:
+    name: E2E - Visual & Styling
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Install Playwright
+        run: npx playwright install --with-deps
+
+      - name: Run E2E tests - Batch 3
+        run: npx playwright test --grep "Visual Regression Tests|Advanced Styling and CSS Tests"
+
+      - name: Upload blob report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: blob-report-batch-3
+          path: blob-report
+          retention-days: 30
+
+  # Batch 4: Cross-Platform & Misc (~6-8 min)
+  e2e-batch-4:
+    name: E2E - Cross-Platform & Misc
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build
+        run: npm run build
+
+      - name: Install Playwright
+        run: npx playwright install --with-deps
+
+      - name: Run E2E tests - Batch 4
+        run: npx playwright test --grep "Cross-Platform UI Consistency|home page"
+
+      - name: Upload blob report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: blob-report-batch-4
+          path: blob-report
+          retention-days: 30
+
+  # Merge and publish test results
+  e2e-results:
+    name: E2E Test Results
+    runs-on: ubuntu-latest
+    needs: [e2e-batch-1, e2e-batch-2, e2e-batch-3, e2e-batch-4]
+    if: always()
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Download all blob reports
+        uses: actions/download-artifact@v4
+        with:
+          path: all-blob-reports
+          pattern: blob-report-*
+
+      - name: Merge reports
+        run: |
+          npx playwright merge-reports --reporter html ./all-blob-reports
+
+      - name: Upload HTML report
+        uses: actions/upload-artifact@v4
+        with:
+          name: html-report
+          path: playwright-report
+          retention-days: 30
+
+      - name: Publish test results summary
+        if: always()
+        run: |
+          echo "## E2E Test Results 🧪" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "- **Batch 1:** Functionality & Components" >> $GITHUB_STEP_SUMMARY
+          echo "- **Batch 2:** Responsive & Mobile" >> $GITHUB_STEP_SUMMARY
+          echo "- **Batch 3:** Visual & Styling" >> $GITHUB_STEP_SUMMARY
+          echo "- **Batch 4:** Cross-Platform & Misc" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "📊 [View detailed HTML report](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }})" >> $GITHUB_STEP_SUMMARY
+
+      - name: Check job statuses
+        if: failure()
+        run: |
+          echo "❌ One or more test batches failed. Check individual batch logs above." >> $GITHUB_STEP_SUMMARY