e2e

Give it a goal. Drive the real thing until you can answer whether it works. Fix what breaks, verify the fix, answer.

Scope

• Goal is whatever the user said, in prose
• Args may be a spec, PRD or plan path: read it for intent, the file is not the target
• Nothing said: scope from git status + git diff --stat, or from the checklist you wrote earlier in the conversation

Wrong surface

The most common way this skill lies:

• green on a page you were logged out of, on the tab next to the right one, on a modal that never opened
• URL is the one you meant, and you are the user you meant to be
• assert on state you watched change, then reload and assert it survived
• what you asserted on is the feature, not a lookalike: editor source text, hidden span, the component's own progress label
• poll a count of the real result nodes. Never the absence of a spinner, never the disappearance of the previous step, an SPA keeps it mounted
• same nodes reused for a new result: poll a discriminating value, the count is green before the numbers change
• the DOM can be right while the pixels are wrong. On canvas, WebGL, maps and charts no DOM assertion proves the render, look at the screenshot

Drive

Testing is always Chrome DevTools MCP. Playwright is for artifacts, nothing else.

MCP (mcp__chrome-devtools__*), always headless. The driver for every verification run:

• clicking through by hand, reading the a11y tree, checking console and network. No script to write
• a long or fiddly flow is not a reason to switch. Click it, don't script it
• one shared browser instance. Running alongside other agents, don't touch it, they will steal each other's tab
• writes only inside its workspace roots, so it cannot save to /tmp. A shot you keep inside a workspace root is still MCP's job

Playwright, always chromium.launch({headless: true}), never headless: false. Artifacts only:

• the recording, and the kept screenshots that go with it, when the destination is outside the MCP workspace roots
• parallel runs, where the one shared MCP instance would collide. Not a preference, the only other exit
• global install, run as NODE_PATH=$(npm root -g) node script.js, CommonJS. Same prefix for the check: NODE_PATH=$(npm root -g) node -e "require.resolve('playwright')", bare node won't find it, and playwright --version can be the Python package
• working dir from mktemp -d /tmp/e2e-XXXXXX. Timestamps collide when agents start together