E2E Testing

Overview

Covers E2E test architecture and patterns using Playwright — how to structure test suites, organize tests, and apply proven patterns for authentication, mocking, visual regression, accessibility auditing, and CI parallelism. Focuses on the WHY and WHEN of test patterns rather than Playwright API specifics.

When to use: Designing test suite architecture, structuring Page Object Models, planning CI sharding strategies, setting up authentication flows, organizing tests with tags and annotations, implementing visual regression workflows, mocking network requests, auditing accessibility.

When NOT to use: Unit testing (use Vitest/Jest), API-only testing (use integration tests), component testing in isolation (use component test runners). For Playwright API details, browser automation, scraping, or troubleshooting Playwright errors, use the playwright skill.

Quick Reference

Pattern	API/Tool	Key Points
Role-based locators	`getByRole`, `getByText`, `getByLabel`	Preferred over CSS/XPath selectors
Page Object Model	Classes in `tests/pages/`	Encapsulate all page-specific locators and actions
Authentication	`storageState` + setup projects	Authenticate once, reuse across tests
Visual regression	`expect(page).toHaveScreenshot()`	Mask dynamic content to prevent flakes
Accessibility audit	`AxeBuilder` from `@axe-core/playwright`	`.withTags()` + `.analyze()` on key flows
Trace debugging	`trace: 'on-first-retry'`	Full DOM snapshots, network logs, and timeline
Network mocking	`page.route()`	Stable tests without third-party dependencies
HAR replay	`page.routeFromHAR()`	High-fidelity mocks from recorded traffic
Image blocking	`page.route('*/.{png,jpg}', abort)`	Speed up tests by skipping images
CI sharding	`--shard=1/4`	Split suite across parallel CI machines
Blob reports	`--reporter=blob` + `merge-reports`	Merge sharded results into a single report
Test tags	`{ tag: ['@smoke'] }`	Filter tests by category with `--grep`
Test steps	`test.step('name', async () => {})`	Group actions in trace viewer and reports
Changed tests only	`--only-changed=$GITHUB_BASE_REF`	Run only test files changed since base branch
Native a11y checks	`toHaveAccessibleName`, `toHaveRole`	Lightweight alternative to full axe-core scans
Git info in reports	`captureGitInfo` reporter option	Link test reports to commits for CI debugging
Web-first assertions	`expect(element).toBeVisible()`	Auto-wait instead of `waitForTimeout`
Fixture composition	`mergeTests()` / `mergeExpects()`	Combine 3+ fixture modules into one `test`
Auto fixtures	`{ auto: true }` on `test.extend()`	Run for every test (logging, screenshots)
Fixture options	`{ option: true }` on `test.extend()`	Configurable via config or `test.use()`
Data-driven tests	`for...of` loop generating `test()` calls	Parameterized tests from arrays or CSV files
Context emulation	`browser.newContext()` options	locale, timezone, colorScheme, offline, isMobile
Two roles in one test	Concurrent `browser.newContext()` calls	Separate storageState per context

Common Mistakes

Mistake	Correct Pattern
Using `page.waitForTimeout()` for element visibility	Use web-first assertions like `expect(element).toBeVisible()` which auto-wait
Writing raw locators directly in test files	Encapsulate all selectors in Page Object Model classes
Testing third-party APIs (Stripe, Auth0) directly	Mock external services with `page.route()` for stable, fast tests
Debugging CI failures with screenshots instead of traces	Configure `trace: 'on-first-retry'` and use Playwright Trace Viewer
Sharing state between tests via global variables	Use a fresh `BrowserContext` per test for full isolation
Running all tests in a single CI job	Use Playwright sharding (`--shard=1/N`) across parallel machines
Using CSS/XPath selectors for element location	Use role-based locators that survive refactors and enforce accessibility
Logging in via UI in every test	Use `storageState` with setup projects to authenticate once
Using `injectAxe`/`checkA11y` from `axe-playwright`	Use `AxeBuilder` from `@axe-core/playwright` with `.analyze()`
Committing `storageState` JSON files to git	Add `playwright/.auth/` to `.gitignore`
Relying on `storageState` for sign-out tests	Sign-out invalidates server session — sign in via UI for each sign-out test
Assuming `storageState` persists sessionStorage	It only saves cookies + localStorage — use `addInitScript()` for sessionStorage
Duplicating test code for locale/currency variants	Use fixture options (`{ option: true }`) with per-project config overrides
Creating fixtures without `mergeTests()` for 3+ modules	Use `mergeTests()` to compose fixture files into a single `test` export

Delegation

Discover which user flows lack E2E coverage: Use Explore agent
Build a full Page Object Model test suite for an application: Use Task agent
Plan a CI sharding strategy for a large test suite: Use Plan agent

For Playwright API details, browser automation, scraping, stealth mode, screenshots/PDFs, Docker deployment, or troubleshooting Playwright errors, use the playwright skill.

e2e-testing

E2E Testing

Overview

Quick Reference

Common Mistakes

Delegation

References