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 Claude Code, 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. Run /ce-setup to install required dependencies." 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. Run /ce-setup to install required dependencies." Then stop.

2. Ask Browser Mode

Pipeline mode (mode:pipeline): Skip this step entirely. Default to headless — no question, no blocking. Proceed directly to step 3.

Manual mode: Ask the user whether to run headed or headless using the platform's blocking question tool: AskUserQuestion in Claude Code (call ToolSearch with select:AskUserQuestion first if its schema isn't loaded), request_user_input in Codex, ask_user in Gemini, ask_user in Pi (requires the pi-ask-user extension). Fall back to presenting options in chat only when no blocking tool exists in the harness or the call errors (e.g., Codex edit modes) — not because a schema load is required. Never silently skip the question:

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 and Claim a Free Port

Pipeline mode only (mode:pipeline): When invoked from LFG or another automated pipeline, always find a port that is actually free — never assume 3000 is available, as multiple agents may be running in parallel on the same machine.

Manual mode (no mode:pipeline): Use the preferred port as-is. Do not scan for alternatives — the user controls their own server.

Determine the preferred port using this priority:

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

In pipeline mode, verify the preferred port is free and scan upward if not. In manual mode, use the preferred port directly.

# Step 1: Determine preferred port
PORT="${EXPLICIT_PORT:-}"
if [ -z "$PORT" ]; then
  PORT=$(grep -Eio '(port\s*[:=]\s*|localhost:)([0-9]{4,5})' AGENTS.md 2>/dev/null | grep -Eo '[0-9]{4,5}' | head -1)
fi
if [ -z "$PORT" ]; then
  PORT=$(grep -Eio '(port\s*[:=]\s*|localhost:)([0-9]{4,5})' CLAUDE.md 2>/dev/null | grep -Eo '[0-9]{4,5}' | head -1)
fi
if [ -z "$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}"

# Step 2 (pipeline mode only): scan for a free port
if [ "${PIPELINE_MODE}" = "1" ]; then
  find_free_port() {
    local p=$1
    while lsof -i ":$p" -sTCP:LISTEN -t >/dev/null 2>&1; do
      p=$((p + 1))
    done
    echo $p
  }
  PORT=$(find_free_port "$PORT")
fi
echo "Using dev server port: $PORT"

Set PIPELINE_MODE=1 in your shell when the argument mode:pipeline is present.

6. Start Dev Server if Not Running, Then Verify

Pipeline mode only: If no server is already listening on $PORT, start one automatically in the background. In manual mode, inform the user and stop.

if lsof -i ":${PORT}" -sTCP:LISTEN -t >/dev/null 2>&1; then
  echo "Server already running on port ${PORT}"
else
  if [ "${PIPELINE_MODE}" = "1" ]; then
    # Auto-start in pipeline — pick the right command for this project
    echo "Starting dev server on port ${PORT}..."
    if [ -f "bin/dev" ]; then
      PORT=${PORT} bin/dev > /tmp/dev-server-${PORT}.log 2>&1 &
    elif [ -f "bin/rails" ]; then
      bin/rails server -p ${PORT} > /tmp/dev-server-${PORT}.log 2>&1 &
    elif [ -f "package.json" ]; then
      PORT=${PORT} npm run dev > /tmp/dev-server-${PORT}.log 2>&1 &
    fi
    # Wait up to 30 seconds for server to become ready
    for i in $(seq 1 30); do
      lsof -i ":${PORT}" -sTCP:LISTEN -t >/dev/null 2>&1 && break
      sleep 1
    done
    if ! lsof -i ":${PORT}" -sTCP:LISTEN -t >/dev/null 2>&1; then
      echo "Server did not start in 30s. Last output:"
      tail -20 /tmp/dev-server-${PORT}.log 2>/dev/null
      exit 1
    fi
  else
    # Manual mode — ask the user to start the server
    echo "Server not running on port ${PORT}"
    echo ""
    echo "Please start your development server:"
    echo "  Rails: bin/dev  or  rails server -p ${PORT}"
    echo "  Node/Next.js: npm run dev"
    echo "  Custom port: run this skill again with --port <your-port>"
    exit 0
  fi
fi

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

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:

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

Ask the user how to proceed:

Test Failed: [route]

Issue: [description]
Console errors: [if any]

How to proceed?
1. Fix now - debug and fix the failing test
2. Skip - continue testing other pages

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

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

Quick Usage Examples

# Test current branch changes (auto-detects port)
/ce-test-browser

# Test specific PR
/ce-test-browser 847

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

# Test on a specific port
/ce-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

ce-test-browser