✨ Add Ember.js SDK for visual testing with Testem (#166)

## Summary

Introduces `@vizzly-testing/ember` package that enables visual
regression testing in Ember.js projects using Testem and Playwright.

- Custom Testem launcher that uses Playwright for browser control
(supports Chromium, Firefox, WebKit)
- `vizzlySnapshot()` helper for capturing screenshots in acceptance
tests
- Automatic viewport sizing and `#ember-testing` container expansion
(captures just the app, not QUnit UI)
- TDD server auto-discovery via `.vizzly/server.json`
- Mobile viewport testing with customizable dimensions
- Test app fixture for SDK development and verification

### Architecture

```
Browser (Ember test)
    │
    │ fetch() to snapshot server
    ▼
Snapshot Server (Node.js)
    │
    │ Playwright screenshot
    │
    │ forward to TDD server
    ▼
Vizzly TDD Server
    │
    │ Compare, save baselines
    ▼
.vizzly/baselines/
```

### Usage

```javascript
// testem.cjs
const { configure } = require('@vizzly-testing/ember');

module.exports = configure({
  cwd: 'dist',
  test_page: 'tests/index.html?hidepassed',
  launch_in_ci: ['Chrome'],
});
```

```javascript
// tests/acceptance/visual-test.js
import { vizzlySnapshot } from '@vizzly-testing/ember/test-support';

test('captures homepage', async function(assert) {
  await visit('/');
  await vizzlySnapshot('homepage');
  await vizzlySnapshot('homepage-mobile', { width: 375, height: 667 });
});
```

## Test plan

- [x] Unit tests for testem-config and snapshot-server
- [x] Integration tests for launcher
- [x] E2E test with real Ember app (`npm run test:ember` in
clients/ember)
- [x] Verified screenshots capture just the app content at correct
viewport sizes

Author: Robdel12

clients/ember/.gitignore

@@ -0,0 +1,8 @@
+# Dependencies
+node_modules/
+
+# Test app build artifacts (keep source, ignore build output)
+test-app/node_modules/
+test-app/dist/
+test-app/.vizzly/
+test-app/tmp/

clients/ember/README.md

@@ -0,0 +1,260 @@
+# @vizzly-testing/ember
+
+Visual testing SDK for Ember.js projects using Testem. Capture screenshots from your acceptance and integration tests and compare them with Vizzly.
+
+## Installation
+
+```bash
+npm install -D @vizzly-testing/ember
+
+# Install browser (Chromium is recommended)
+npx playwright install chromium
+```
+
+## Setup
+
+### 1. Configure Testem
+
+Wrap your `testem.js` configuration with the `configure()` function:
+
+```javascript
+// testem.js (or testem.cjs for ES modules projects)
+const { configure } = require('@vizzly-testing/ember');
+
+module.exports = configure({
+  // For Ember with Vite/Embroider, Testem must serve from dist/
+  cwd: 'dist',
+  test_page: 'tests/index.html?hidepassed',
+  disable_watching: true,
+  launch_in_ci: ['Chrome'],
+  launch_in_dev: ['Chrome']
+});
+```
+
+The `configure()` function replaces standard browser launchers (Chrome, Firefox, Safari) with Playwright-powered launchers that can capture screenshots.
+
+> **Note for Ember + Vite projects**: The `cwd: 'dist'` option is required because Vite builds test files into the `dist/` directory. Without this, Testem won't find your test assets.
+
+### 2. Write Tests with Snapshots
+
+Import `vizzlySnapshot` in your test files:
+
+```javascript
+// tests/acceptance/dashboard-test.js
+import { module, test } from 'qunit';
+import { visit } from '@ember/test-helpers';
+import { setupApplicationTest } from 'ember-qunit';
+import { vizzlySnapshot } from '@vizzly-testing/ember/test-support';
+
+module('Acceptance | Dashboard', function(hooks) {
+  setupApplicationTest(hooks);
+
+  test('renders empty state', async function(assert) {
+    await visit('/dashboard');
+
+    // Capture screenshot
+    await vizzlySnapshot('dashboard-empty');
+
+    assert.dom('[data-test-empty-state]').exists();
+  });
+
+  test('renders with data', async function(assert) {
+    // ... setup data
+    await visit('/dashboard');
+
+    // Capture specific element
+    await vizzlySnapshot('dashboard-table', {
+      selector: '[data-test-data-table]'
+    });
+
+    assert.dom('[data-test-data-table]').exists();
+  });
+});
+```
+
+### 3. Run Tests with Vizzly
+
+```bash
+# Start the Vizzly TDD server
+vizzly tdd start
+
+# Build with development mode (includes test files)
+npm run build -- --mode development
+
+# Run your tests via Testem
+npx testem ci --file testem.cjs
+
+# Or use ember test (which handles the build)
+ember test
+```
+
+Screenshots are captured and compared locally. View results in the Vizzly dashboard at http://localhost:47392.
+
+## API
+
+### `configure(testemConfig)`
+
+Wraps your Testem configuration to use Vizzly-powered browser launchers.
+
+```javascript
+const { configure } = require('@vizzly-testing/ember');
+
+module.exports = configure({
+  // Your existing testem.js options
+  launch_in_ci: ['Chrome'],
+  launch_in_dev: ['Chrome'],
+});
+```
+
+**Browser Mapping:**
+- `Chrome` → Uses Playwright Chromium
+- `Firefox` → Uses Playwright Firefox
+- `Safari` / `WebKit` → Uses Playwright WebKit
+
+### `vizzlySnapshot(name, options?)`
+
+Captures a screenshot and sends it to Vizzly for comparison. By default, captures just the `#ember-testing` container (your app), not the QUnit test runner UI.
+
+```javascript
+import { vizzlySnapshot } from '@vizzly-testing/ember/test-support';
+
+// Basic usage - captures app at 1280x720
+await vizzlySnapshot('homepage');
+
+// Mobile viewport
+await vizzlySnapshot('homepage-mobile', {
+  width: 375,
+  height: 667
+});
+
+// Capture specific element within the app
+await vizzlySnapshot('login-form', {
+  selector: '[data-test-login-form]'
+});
+
+// Full options
+await vizzlySnapshot('screenshot-name', {
+  // Viewport dimensions (default: 1280x720)
+  width: 1280,
+  height: 720,
+
+  // Capture specific element within #ember-testing
+  selector: '[data-test-component]',
+
+  // What to capture: 'app' (default), 'container', or 'page'
+  scope: 'app',
+
+  // Capture full scrollable content
+  fullPage: false,
+
+  // Add custom metadata
+  properties: {
+    theme: 'dark',
+    user: 'admin'
+  }
+});
+```
+
+**Options:**
+
+| Option | Type | Default | Description |
+|--------|------|---------|-------------|
+| `width` | number | 1280 | Viewport width for the screenshot |
+| `height` | number | 720 | Viewport height for the screenshot |
+| `selector` | string | null | CSS selector to capture specific element |
+| `scope` | string | 'app' | What to capture: `'app'` (just #ember-testing), `'container'`, or `'page'` (full page including QUnit) |
+| `fullPage` | boolean | false | Capture full scrollable content |
+| `properties` | object | {} | Custom metadata attached to the snapshot |
+
+The function automatically:
+- Waits for Ember's `settled()` before capturing
+- Expands the `#ember-testing` container to the specified viewport size
+- Captures just your app content (not the QUnit UI)
+
+### `isVizzlyAvailable()`
+
+Check if Vizzly is available in the current test environment.
+
+```javascript
+import { isVizzlyAvailable } from '@vizzly-testing/ember/test-support';
+
+if (isVizzlyAvailable()) {
+  await vizzlySnapshot('conditional-snapshot');
+}
+```
+
+## Browser Support
+
+| Browser | Status |
+|---------|--------|
+| Chromium (Chrome, Edge) | Fully supported |
+| Firefox | Supported |
+| WebKit (Safari) | Supported |
+
+Install browsers with:
+
+```bash
+npx playwright install chromium
+npx playwright install firefox
+npx playwright install webkit
+```
+
+## How It Works
+
+1. **Testem Configuration**: The `configure()` wrapper replaces standard browser launchers with custom Vizzly launchers
+2. **Custom Launcher**: When Testem starts, it spawns `vizzly-browser` instead of the regular browser
+3. **Playwright Integration**: The launcher uses Playwright to control the browser and capture screenshots
+4. **Snapshot Server**: A local HTTP server receives screenshot requests from test code
+5. **Vizzly Integration**: Screenshots are forwarded to the Vizzly TDD server for comparison
+
+## CI/CD
+
+For CI environments, ensure:
+
+1. Browsers are installed: `npx playwright install chromium`
+2. Vizzly token is set: `VIZZLY_TOKEN=your-token`
+
+```yaml
+# GitHub Actions example
+- name: Install Playwright
+  run: npx playwright install chromium
+
+- name: Run Tests
+  env:
+    VIZZLY_TOKEN: ${{ secrets.VIZZLY_TOKEN }}
+  run: ember test
+```
+
+## Troubleshooting
+
+### "No snapshot server available"
+
+Tests must be run through Testem with the Vizzly-configured launchers. Ensure:
+- `testem.js` uses `configure()` wrapper
+- Running via `ember test` (not direct browser)
+
+### "No Vizzly server found"
+
+Start the TDD server before running tests:
+
+```bash
+vizzly tdd start
+```
+
+### Browser fails to launch
+
+Install the required browser:
+
+```bash
+npx playwright install chromium
+```
+
+For CI environments, you may need additional dependencies:
+
+```bash
+npx playwright install-deps chromium
+```
+
+## License
+
+MIT

clients/ember/bin/vizzly-browser.js

@@ -0,0 +1,116 @@
+#!/usr/bin/env node
+/**
+ * Vizzly Browser Launcher
+ *
+ * Custom browser launcher spawned by Testem. Uses Playwright to launch
+ * a browser with screenshot capture capabilities.
+ *
+ * Usage: vizzly-browser <browser> <url>
+ *   browser: chromium | firefox | webkit
+ *   url: The test page URL (provided by Testem)
+ *
+ * @example
+ * # Testem spawns this command:
+ * npx vizzly-browser chromium http://localhost:7357/tests/index.html
+ */
+
+import { closeBrowser, launchBrowser } from '../src/launcher/browser.js';
+import {
+  setPage,
+  startSnapshotServer,
+  stopSnapshotServer,
+} from '../src/launcher/snapshot-server.js';
+
+let [, , browserType, testUrl] = process.argv;
+
+// Validate arguments
+if (!browserType || !testUrl) {
+  console.error('Usage: vizzly-browser <browser> <url>');
+  console.error('  browser: chromium | firefox | webkit');
+  console.error('  url: Test page URL (provided by Testem)');
+  process.exit(1);
+}
+
+let browserInstance = null;
+let snapshotServer = null;
+let isShuttingDown = false;
+
+/**
+ * Clean up resources and exit
+ */
+async function cleanup() {
+  if (isShuttingDown) return;
+  isShuttingDown = true;
+
+  try {
+    if (browserInstance) {
+      await closeBrowser(browserInstance);
+    }
+  } catch (error) {
+    console.error('[vizzly-browser] Error closing browser:', error.message);
+  }
+
+  try {
+    if (snapshotServer) {
+      await stopSnapshotServer(snapshotServer);
+    }
+  } catch (error) {
+    console.error('[vizzly-browser] Error stopping server:', error.message);
+  }
+
+  process.exit(0);
+}
+
+/**
+ * Main launcher function
+ */
+async function main() {
+  try {
+    // 1. Start snapshot server first
+    snapshotServer = await startSnapshotServer();
+    let snapshotUrl = `http://127.0.0.1:${snapshotServer.port}`;
+
+    // 2. Launch browser with Playwright
+    // Note: We set the page reference in launchBrowser before navigation
+    // to avoid a race condition where tests run before page is set
+    browserInstance = await launchBrowser(browserType, testUrl, {
+      snapshotUrl,
+      onPageCreated: page => {
+        // Set page reference immediately when page is created
+        // This happens BEFORE navigation so tests can capture screenshots
+        setPage(page);
+      },
+    });
+
+    // 3. Keep process alive - Testem will send SIGTERM when done
+    // The browser will run tests and the snapshot server will handle requests
+    await new Promise(() => {});
+  } catch (error) {
+    console.error('[vizzly-browser] Failed to start:', error.message);
+
+    // Attempt cleanup before exiting
+    if (snapshotServer) {
+      await stopSnapshotServer(snapshotServer).catch(() => {});
+    }
+
+    process.exit(1);
+  }
+}
+
+// Handle graceful shutdown signals from Testem
+process.on('SIGTERM', cleanup);
+process.on('SIGINT', cleanup);
+process.on('SIGHUP', cleanup);
+
+// Handle unexpected errors
+process.on('uncaughtException', error => {
+  console.error('[vizzly-browser] Uncaught exception:', error.message);
+  cleanup();
+});
+
+process.on('unhandledRejection', reason => {
+  console.error('[vizzly-browser] Unhandled rejection:', reason);
+  cleanup();
+});
+
+main();