test-browser

Run end-to-end browser tests on pages affected by a PR or branch changes using agent-browser CLI.

CRITICAL: Use agent-browser CLI Only

DO NOT use Chrome MCP tools (mcp__claude-in-chrome__*).

This command uses the agent-browser CLI exclusively. The agent-browser CLI is a Bash-based tool from Vercel that runs headless Chromium. It is NOT the same as Chrome browser automation via MCP.

If you find yourself calling mcp__claude-in-chrome__* tools, STOP. Use agent-browser Bash commands instead.

Introduction

Role: QA Engineer specializing in browser-based end-to-end testing

This command tests affected pages in a real browser, catching issues that unit tests miss:

• JavaScript integration bugs
• CSS/layout regressions
• User workflow breakages
• Console errors

Prerequisites

• Local development server running (e.g., bin/dev, rails server, npm run dev)
• agent-browser CLI installed (see Setup below)
• Git repository with changes to test

Setup

Check installation:

command -v agent-browser >/dev/null 2>&1 && echo "Installed" || echo "NOT INSTALLED"

Install if needed:

npm install -g agent-browser
agent-browser install  # Downloads Chromium (~160MB)

See the CLI reference below for detailed usage.

Main Tasks

0. Verify agent-browser Installation

Before starting ANY browser testing, verify agent-browser is installed:

command -v agent-browser >/dev/null 2>&1 && echo "Ready" || (echo "Installing..." && npm install -g agent-browser && agent-browser install)

If installation fails, inform the user and stop.

1. Ask Browser Mode

Before starting tests, ask user if they want to watch the browser:

Use ask-questions-if-underspecified with:

• Question: "Do you want to watch the browser tests run?"
• Options:
  1. Headed (watch) - Opens visible browser window so you can see tests run
  2. Headless (faster) - Runs in background, faster but invisible

Store the choice and use --headed flag when user selects "Headed".

2. Determine Test Scope

Test target: $ARGUMENTS

If PR number provided:

gh pr view [number] --json files -q '.files[].path'

If 'current' or empty:

git diff --name-only main...HEAD

If branch name provided:

git diff --name-only main...[branch]

3. Map Files to Routes

Map changed files to testable routes:

| File Pattern | Route(s) | |-------------|----------| | app/views/users/* | /users, /users/:id, /users/new | | app/controllers/settings_controller.rb | /settings | | app/javascript/controllers/*_controller.js | Pages using that Stimulus controller | | app/components/*_component.rb | Pages rendering that component | | app/views/layouts/* | All pages (test homepage at minimum) | | app/assets/stylesheets/* | Visual regression on key pages | | app/helpers/*_helper.rb | Pages using that helper | | src/app/* (Next.js) | Corresponding routes | | src/components/* | Pages using those components |

Build a list of URLs to test based on the mapping.

4. Verify Server is Running

Before testing, verify the local server is accessible:

agent-browser open http://localhost:3000
agent-browser snapshot -i

If server is not running, inform user:

**Server not running**

Please start your development server:
- Rails: `bin/dev` or `rails server`
- Node/Next.js: `npm run dev`

Then run `/test-browser` again.

5. Test Each Affected Page

For each affected route, use agent-browser CLI commands (NOT Chrome MCP):

Step 1: Navigate and capture snapshot

agent-browser open "http://localhost:3000/[route]"
agent-browser snapshot -i

Step 2: For headed mode (visual debugging)

agent-browser --headed open "http://localhost:3000/[route]"
agent-browser --headed snapshot -i

Step 3: Verify key elements

• Use agent-browser snapshot -i to get interactive elements with refs
• Page title/heading present
• Primary content rendered
• No error messages visible
• Forms have expected fields

Step 4: Test critical interactions

agent-browser click @e1  # Use ref from snapshot
agent-browser snapshot -i

Step 5: Take screenshots

agent-browser screenshot page-name.png
agent-browser screenshot --full page-name-full.png  # Full page

6. Human Verification (When Required)

Pause for human input when testing touches:

| Flow Type | What to Ask | |-----------|-------------| | OAuth | "Please sign in with [provider] and confirm it works" | | Email | "Check your inbox for the test email and confirm receipt" | | Payments | "Complete a test purchase in sandbox mode" | | SMS | "Verify you received the SMS code" | | External APIs | "Confirm the [service] integration is working" |

Use ask-questions-if-underspecified:

**Human Verification Needed**

This test touches the [flow type]. Please:
1. [Action to take]
2. [What to verify]

Did it work correctly?
1. Yes - continue testing
2. No - describe the issue

7. Handle Failures

When a test fails:

1. Document the failure:

   • Screenshot the error state: agent-browser screenshot error.png
   • Note the exact reproduction steps

2. Ask user how to proceed:

   **Test Failed: [route]**
   
   Issue: [description]
   Console errors: [if any]
   
   How to proceed?
   1. Fix now - I'll help debug and fix
   2. Create todo - Add to todos/ for later
   3. Skip - Continue testing other pages
   

3. If "Fix now":

   • Investigate the issue
   • Propose a fix
   • Apply fix
   • Re-run the failing test

4. If "Create todo":

   • Create {id}-pending-p1-browser-test-{description}.md
   • Continue testing

5. If "Skip":

   • Log as skipped
   • Continue testing

8. Test Summary

After all tests complete, present summary:

## Browser Test Results

**Test Scope:** PR #[number] / [branch name]
**Server:** http://localhost:3000

### Pages Tested: [count]

| Route | Status | Notes |
|-------|--------|-------|
| `/users` | Pass | |
| `/settings` | Pass | |
| `/dashboard` | Fail | Console error: [msg] |
| `/checkout` | Skip | Requires payment credentials |

### Console Errors: [count]
- [List any errors found]

### Human Verifications: [count]
- OAuth flow: Confirmed
- Email delivery: Confirmed

### Failures: [count]
- `/dashboard` - [issue description]

### Created Todos: [count]
- `005-pending-p1-browser-test-dashboard-error.md`

### Result: [PASS / FAIL / PARTIAL]

Quick Usage Examples

# Test current branch changes
/test-browser

# Test specific PR
/test-browser 847

# Test specific branch
/test-browser feature/new-dashboard

agent-browser CLI Reference

ALWAYS use these Bash commands. NEVER use mcp__claude-in-chrome__ tools.*

# Navigation
agent-browser open <url>           # Navigate to URL
agent-browser back                 # Go back
agent-browser close                # Close browser

# Snapshots (get element refs)
agent-browser snapshot -i          # Interactive elements with refs (@e1, @e2, etc.)
agent-browser snapshot -i --json   # JSON output

# Interactions (use refs from snapshot)
agent-browser click @e1            # Click element
agent-browser fill @e1 "text"      # Fill input
agent-browser type @e1 "text"      # Type without clearing
agent-browser press Enter          # Press key

# Screenshots
agent-browser screenshot out.png       # Viewport screenshot
agent-browser screenshot --full out.png # Full page screenshot

# Headed mode (visible browser)
agent-browser --headed open <url>      # Open with visible browser
agent-browser --headed click @e1       # Click in visible browser

# Wait
agent-browser wait @e1             # Wait for element
agent-browser wait 2000            # Wait milliseconds