SmartUI Visual Regression Skill

Core Patterns

Playwright + SmartUI SDK

javascript

const { chromium } = require('playwright');
const { smartuiSnapshot } = require('@lambdatest/smartui-cli');

(async () => {
  const browser = await chromium.launch();
  const page = await browser.newPage();

  await page.goto('https://example.com');
  await smartuiSnapshot(page, 'Homepage');

  await page.goto('https://example.com/login');
  await smartuiSnapshot(page, 'Login Page');

  await browser.close();
})();

Selenium + SmartUI

java

// Take SmartUI screenshot
((JavascriptExecutor) driver).executeScript(
    "smartui.takeScreenshot=Login Page"
);

CLI Execution

bash

# Install
npm install @lambdatest/smartui-cli --save-dev

# Configure
npx smartui config:create smartui.config.json

# Execute
npx smartui exec -- node test.js
# or with Playwright
npx smartui exec -- npx playwright test

smartui.config.json

json

{
  "web": {
    "browsers": ["chrome", "firefox", "safari"],
    "viewports": [[1920, 1080], [1366, 768], [375, 812]]
  },
  "waitForPageRender": 5000,
  "waitForTimeout": 1000
}

SmartUI with Storybook

bash

npx smartui storybook http://localhost:6006 --config smartui.config.json

Approval Workflow

•First run creates baseline screenshots
•Subsequent runs compare against baseline
•Differences highlighted in dashboard
•Approve/reject changes in LambdaTest SmartUI dashboard
•Approved screenshots become new baseline

Anti-Patterns

Bad	Good	Why
No viewport config	Multiple viewports	Responsive issues
No wait for render	`waitForPageRender`	Incomplete screenshots
Screenshot everything	Key pages/components	Noise reduction
No approval process	Review diffs in dashboard	Catch regressions

Cloud Authentication

Set environment variables:

bash

export PROJECT_TOKEN="your-smartui-project-token"   # From SmartUI dashboard
export LT_USERNAME="your-username"                   # For Selenium/Playwright cloud
export LT_ACCESS_KEY="your-access-key"               # For Selenium/Playwright cloud

CLI approach (uses PROJECT_TOKEN):

bash

npx smartui exec -- npx playwright test

Selenium Cloud approach (uses LT_USERNAME/LT_ACCESS_KEY):

java

// Capabilities include SmartUI options
HashMap<String, Object> ltOptions = new HashMap<>();
ltOptions.put("user", System.getenv("LT_USERNAME"));
ltOptions.put("accessKey", System.getenv("LT_ACCESS_KEY"));
ltOptions.put("build", "SmartUI Build");
ltOptions.put("smartUI.project", "My SmartUI Project");
ChromeOptions options = new ChromeOptions();
options.setCapability("LT:Options", ltOptions);
WebDriver driver = new RemoteWebDriver(
    new URL("https://hub.lambdatest.com/wd/hub"), options);

Quick Reference

Task	Command
Install	`npm install @lambdatest/smartui-cli`
Init config	`npx smartui config:create smartui.config.json`
Run	`npx smartui exec -- <test command>`
Storybook	`npx smartui storybook <url>`
Dashboard	`https://smartui.lambdatest.com`

Deep Patterns

For advanced patterns, debugging guides, CI/CD integration, and best practices, see reference/playbook.md.