Browser Testing with Screenshots

Overview

Automate Chrome browser testing with visual verification using browser-tools. Connect to Chrome DevTools Protocol for navigation, interaction, and screenshot capture to confirm application functionality.

Prerequisites

REQUIRED: Install agent-tools from https://github.com/badlogic/agent-tools

bash
# Clone and install agent-tools
git clone https://github.com/badlogic/agent-tools.git
cd agent-tools
# Follow installation instructions in the repository
# Ensure all executables (browser-start.js, browser-nav.js, etc.) are in your PATH

Verify installation:

bash
# Check that browser tools are available
which browser-start.js
which browser-nav.js
which browser-screenshot.js

All browser-\ commands referenced in this skill come from the agent-tools repository and must be properly installed and accessible in your system PATH.

When to Use

Use this skill when:

• Testing web application UI flows
• Verifying visual changes or layouts
• Automating repetitive browser interactions
• Documenting application behavior with screenshots
• Testing localhost applications during development
• Need to interact with elements that require human-like selection

Don't use for:

• API testing (use direct HTTP calls)
• Headless testing where visuals don't matter
• Simple page content validation (use curl/wget)

Quick Reference

| Task | Command | Purpose | | --------------- | ------------------------------------------------ | ----------------------------- | | Start browser | browser-start.js | Launch Chrome with debugging | | Navigate | browser-nav.js http://localhost:5172/dashboard | Go to specific URL | | Take screenshot | browser-screenshot.js | Capture current viewport | | Pick elements | browser-pick.js "Select the login button" | Interactive element selection | | Run JavaScript | browser-eval.js 'document.title' | Execute code in page context | | Extract content | browser-content.js | Get readable page content | | View cookies | browser-cookies.js | List session cookies |

Setup and Basic Workflow

1. Start Chrome with Remote Debugging

bash
# Launch Chrome with debugging enabled (preserves user profile)
browser-start.js

# Or start fresh (no cookies, clean state)
browser-start.js --fresh

Expected Result: Chrome opens on port 9222 with DevTools Protocol enabled

2. Navigate to Application

bash
# Go to your application starting point
browser-nav.js http://localhost:5172/dashboard

Verify: Browser navigates to dashboard page

3. Capture Baseline Screenshot

bash
# Take initial screenshot to confirm page loaded
browser-screenshot.js

Output: Returns path to screenshot file (e.g., screenshot_20231203_141532.png)

Testing Workflow with Screenshots

Complete Test Scenario Example

bash
#!/bin/bash
# Test login and dashboard functionality

echo "🚀 Starting browser test..."

# 1. Launch browser
browser-start.js --fresh

# 2. Navigate to login page
browser-nav.js http://localhost:5172/login
sleep 2

# 3. Take screenshot of login page
LOGIN_SHOT=$(browser-screenshot.js)
echo "📸 Login page: $LOGIN_SHOT"

# 4. Fill login form (interactive element picking)
browser-pick.js "Click the username field"
browser-eval.js 'document.activeElement.value = "testuser"'

browser-pick.js "Click the password field"
browser-eval.js 'document.activeElement.value = "password123"'

# 5. Screenshot filled form
FORM_SHOT=$(browser-screenshot.js)
echo "📸 Filled form: $FORM_SHOT"

# 6. Submit form
browser-pick.js "Click the login button"
sleep 3

# 7. Verify dashboard loaded
browser-nav.js http://localhost:5172/dashboard
DASHBOARD_SHOT=$(browser-screenshot.js)
echo "📸 Dashboard: $DASHBOARD_SHOT"

# 8. Verify specific dashboard elements
browser-pick.js "Select the navigation menu"
browser-eval.js 'console.log("Navigation found:", !!document.querySelector(".nav"))'

echo "✅ Test complete. Screenshots saved."

Element Interaction Pattern

bash
# Interactive element selection (best for dynamic content)
browser-pick.js "Select the submit button"
# User clicks element in browser → returns CSS selector

# Use returned selector for automation
SELECTOR=$(browser-pick.js "Select the submit button" | grep "selector:")
browser-eval.js "document.querySelector('$SELECTOR').click()"

# Take screenshot to verify action
browser-screenshot.js

Advanced Usage

JavaScript Evaluation for Complex Interactions

bash
# Check if element exists before interaction
browser-eval.js 'document.querySelector("#login-form") !== null'

# Wait for dynamic content
browser-eval.js '
  new Promise(resolve => {
    const check = () => {
      if (document.querySelector(".loaded")) resolve(true);
      else setTimeout(check, 100);
    };
    check();
  })
'

# Extract form data
browser-eval.js 'JSON.stringify(Object.fromEntries(new FormData(document.querySelector("form"))))'

Screenshot with Timing

bash
# Navigate and wait before screenshot
browser-nav.js http://localhost:5172/slow-page
sleep 5  # Wait for animations/loading
browser-screenshot.js

Content Extraction for Verification

bash
# Get page title
PAGE_TITLE=$(browser-eval.js 'document.title')
echo "Current page: $PAGE_TITLE"

# Extract readable content
browser-content.js > page_content.md

# Check for specific text
browser-eval.js 'document.body.textContent.includes("Welcome to Dashboard")'

Common Mistakes

| Mistake | Problem | Solution | | ------------------------- | ----------------------------- | --------------------------------------------- | | No sleep after navigation | Screenshots of loading page | Add sleep 2-5 after nav | | Hardcoded selectors | Breaks when UI changes | Use browser-pick.js for selection | | Missing Chrome setup | "Connection refused" errors | Run browser-start.js first | | Wrong localhost port | Navigation fails | Verify application is running on correct port | | Screenshot timing | Captures before content loads | Wait for page load or specific elements | | Not preserving state | Login lost between commands | Use default profile, not --fresh |

Error Handling

bash
# Check if Chrome is running
if ! browser-eval.js 'true' 2>/dev/null; then
  echo "❌ Chrome not connected. Running browser-start.js..."
  browser-start.js
fi

# Verify navigation succeeded
if browser-eval.js 'location.href.includes("dashboard")'; then
  echo "✅ Navigation successful"
else
  echo "❌ Navigation failed"
  exit 1
fi

File Output Patterns

• Screenshots: screenshot_YYYYMMDD_HHMMSS.png in current directory
• Content: Markdown format via stdout from browser-content.js
• Selectors: CSS selectors from browser-pick.js interaction
• JavaScript results: JSON or string values from browser-eval.js

Integration with Testing Frameworks

bash
# Create test evidence directory
mkdir -p test-results/$(date +%Y%m%d_%H%M%S)
cd test-results/$(date +%Y%m%d_%H%M%S)

# Run tests with organized screenshots
browser-start.js
for page in login dashboard profile; do
  browser-nav.js "http://localhost:5172/$page"
  sleep 2
  screenshot=$(browser-screenshot.js)
  mv "$screenshot" "${page}_page.png"
  echo "✅ $page page tested"
done

Real-World Impact

Benefits:

• Visual verification: Screenshots provide immediate feedback on UI state
• Interactive debugging: Element picker works with dynamic/complex selectors
• State preservation: Maintains login sessions between commands
• Evidence collection: Automated screenshot capture for test documentation
• Development workflow: Quick verification of localhost changes

Results:

• Faster UI testing iteration (visual confirmation vs manual checking)
• Reliable element selection (human picks, automation uses)
• Test documentation with visual proof
• Catches visual regressions immediately

Key principle: Combine automated navigation with human element selection for robust, maintainable browser testing.