loom-e2e-testing

# E2E Testing ## Overview Browser E2E validates full user journeys. This file owns **selectors, auto-waiting, network interception, POM, browser flakiness, and trace/video debugging** (Playwright-first, Cypress noted where it differs). E2E is the *tip* of the pyramid — keep it thin and reserve it for critical paths; push logic down to unit/integration (`loom-test-strategy`). For test-double taxonomy and AAA see `loom-testing`. ## Framework choice Default to **Playwright** for new suites: true multi-browser (incl. WebKit/Safari), multi-tab/origin, out-of-process network interception, built-in parallelism and trace viewer, and non-JS bindings (Python/.NET/Java). Choose **Cypress** only when the team is already invested or wants its live time-travel debugger; its in-browser model limits multi-tab, cross-origin, and true WebKit. Selenium/Puppeteer: legacy or Chrome-only automation, not greenfield E2E. ```bash npm init playwright@latest # scaffolds config + CI + browsers ``` ```typescript // playwright.config.ts — the load-bearing knobs export default defineConfig({ testDir: "./e2e", fullyParallel: true, // parallel within files too forbidOnly: !!process.env.CI, // fail CI if a .only slips in retries: process.env.CI ? 2 : 0, // retry ONLY to surface flakes reporter: [["html"], ["junit", { outputFile: "results.xml" }]], use: { baseURL: "http://localhost:3000", trace: "on-first-retry", // ...