marcusrbrown/test-browser

Browser Test Skill

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

Use agent-browser Only For Browser Automation

This workflow uses the agent-browser CLI exclusively. Do not use any alternative browser automation system, browser MCP integration, or built-in browser-control tool. If the platform offers multiple ways to control a browser, always choose agent-browser.

Use agent-browser for: opening pages, clicking elements, filling forms, taking screenshots, and scraping rendered content.

Platform-specific hints:

• In OpenCode, do not use Chrome MCP tools (mcp__claude-in-chrome__*).
• In Codex, do not substitute unrelated browsing tools.

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 whether agent-browser is installed:

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

If not installed, inform the user: "agent-browser is not installed. Install it with npm install -g agent-browser." Then stop — this skill cannot function without agent-browser.

Workflow

1. Verify Installation

Before starting, verify agent-browser is available:

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

If not installed, inform the user: "agent-browser is not installed. Install it with npm install -g agent-browser." Then stop.

2. Ask Browser Mode

Ask the user whether to run headed or headless (using the platform's question tool — e.g., question in OpenCode, request_user_input in Codex, ask_user in Gemini — or present options and wait for a reply):

Do you want to watch the browser tests run?

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 the --headed flag when the user selects option 1.

3. Determine Test Scope

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]

4. 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.

5. Detect Dev Server Port

Determine the dev server port using this priority:

1. Explicit argument — if the user passed --port 5000, use that directly
2. Project instructions — check AGENTS.md, AGENTS.md, or other instruction files for port references
3. package.json — check dev/start scripts for --port flags
4. Environment files — check .env, .env.local, .env.development for PORT=
5. Default — fall back to 3000

PORT="${EXPLICIT_PORT:-}"
if [ -z "$PORT" ]; then
  PORT=$(grep -Eio '(port\s*[:=]\s*|localhost:)([0-9]{4,5})' AGENTS.md 2>/dev/null | grep -Eo '[0-9]{4,5}' | head -1)
  if [ -z "$PORT" ]; then
    PORT=$(grep -Eio '(port\s*[:=]\s*|localhost:)([0-9]{4,5})' AGENTS.md 2>/dev/null | grep -Eo '[0-9]{4,5}' | head -1)
  fi
fi
if [ -z "$PORT" ]; then
  PORT=$(grep -Eo '\-\-port[= ]+[0-9]{4,5}' package.json 2>/dev/null | grep -Eo '[0-9]{4,5}' | head -1)
fi
if [ -z "$PORT" ]; then
  PORT=$(grep -h '^PORT=' .env .env.local .env.development 2>/dev/null | tail -1 | cut -d= -f2)
fi
PORT="${PORT:-3000}"
echo "Using dev server port: $PORT"

6. Verify Server is Running

agent-browser open http://localhost:${PORT}
agent-browser snapshot -i

If the server is not running, inform the user:

Server not running on port ${PORT}

Please start your development server:
- Rails: `bin/dev` or `rails server`
- Node/Next.js: `npm run dev`
- Custom port: run this skill again with `--port <your-port>`

Then re-run this skill.

7. Test Each Affected Page

For each affected route:

Navigate and capture snapshot:

agent-browser open "http://localhost:${PORT}/[route]"
agent-browser snapshot -i

For headed mode:

agent-browser --headed open "http://localhost:${PORT}/[route]"
agent-browser --headed snapshot -i

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

Test critical interactions:

agent-browser click @e1
agent-browser snapshot -i

Take screenshots:

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

8. Human Verification (When Required)

Pause for human input when testing touches flows that require external interaction:

| 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" |

Ask the user (using the platform's question tool, or present numbered options and wait):

Human Verification Needed

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

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

9. 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 the 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 a todo for later (using the todo-create skill)
   3. Skip - Continue testing other pages
   

3. If "Fix now": investigate, propose a fix, apply, re-run the failing test

4. If "Create todo": load the todo-create skill and create a todo with priority p1 and description browser-test-{description}, continue

5. If "Skip": log as skipped, continue

10. Test Summary

After all tests complete, present a summary:

## Browser Test Results

**Test Scope:** PR #[number] / [branch name]
**Server:** http://localhost:${PORT}

### 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 (auto-detects port)
/test-browser

# Test specific PR
/test-browser 847

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

# Test on a specific port
/test-browser --port 5000

agent-browser CLI Reference

Run agent-browser --help for all commands.

Key commands:

# 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