The single most important flow in my app is: a stranger lands on the site, signs up, and becomes a paying customer. I want an end-to-end test that proves this works. Set up a browser-level test (Playwright, Cypress, or whatever fits my stack; recommend one if I have none and wait for my go-ahead) that walks the real flow: 1. Load the landing page and follow the signup call to action. 2. Complete signup with a fresh test account. 3. Verify any required email confirmation step, using a test inbox or intercepted email. 4. Navigate to the pricing or upgrade page. 5. Complete checkout using the payment provider's test card numbers. 6. Assert the account now shows as paid: correct plan in the UI, correct state in the database, receipt or welcome email triggered. Then write the negative variant: a declined test card at checkout should show a clear error to the user and must not grant access to paid features. Keep the test data isolated. It should create its own account and clean up after itself, or run only against a dedicated test environment. It must never run against production. When done, run it and show me the result. If any step fails, show me the exact step and the page state at failure, because a broken step here is a launch blocker, not a test problem.