E2e Playwright Testing

E2E Playwright Testing

Patterns and conventions for reliable end-to-end browser testing with Playwright.

Comprehensive E2E testing guide for web applications. Contains 8 rules across 6 categories covering locator strategies, authentication reuse, form testing (including React/SPA-specific gotchas), assertions, test organization, reliability, and CI/CD configuration.

Stack Detection

Before writing or reviewing E2E tests, detect the project stack:

Step 1 — Check for Playwright

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# Look in package.json devDependencies:
# "@playwright/test" → Playwright is installed
# Check for playwright.config.js or playwright.config.ts

• If @playwright/test is present → use Playwright patterns from this skill
• If cypress is present → this skill does not apply

Step 2 — Detect Frontend Framework

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# Check package.json dependencies:
# "react" + "@inertiajs/react" → React + Inertia.js (SPA with server routing)
# "react" + "react-router" → React SPA
# "vue" → Vue.js
# "next" → Next.js

Why this matters:

• React + Inertia.js: Use waitForURL not waitForLoadState('networkidle') — Inertia uses history.pushState
• React controlled inputs: fill() works for text but keyboard.type() needed for date/time
• SPA navigation: Page doesn't do full reload — assertions must wait for content, not network idle

Step 3 — Detect Auth Pattern

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# Check for session-based (Laravel Sanctum) or token-based (JWT) auth
# Session: storageState saves cookies
# Token: may need to save tokens to localStorage

Step 4 — Detect Rate Limiting

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# Check routes for throttle middleware
# If present in dev, tests will hit 429 after ~5 login attempts
# Solution: production-only throttle or increase limits in test env

Metadata

• Version: 1.0.0
• Rule Count: 8 rules across 6 categories
• License: MIT

When to Apply

• Writing or reviewing Playwright E2E tests
• Setting up E2E testing for a new project
• Debugging flaky browser tests
• Testing form submissions, authentication flows, or user interactions
• Choosing locator strategies for elements
• Configuring Playwright for CI/CD

Rule Categories by Priority

Quick Reference

1. Locators (CRITICAL)

• loc-prefer-role-locators - Use getByRole/getByLabel over CSS selectors
• loc-strict-mode - Handle strict mode violations with exact/first/scoped

2. Authentication (CRITICAL)

• auth-storage-state - Reuse login state via setup project pattern

3. Assertions (HIGH)

• assert-web-first - Use auto-retrying expect(locator) assertions

4. Forms & Inputs (HIGH)

• form-react-date-inputs - Use keyboard.type() for date/time in React apps
• form-custom-checkboxes - Handle sr-only checkbox components

5. Test Organization (MEDIUM)

• org-mirror-routes - Directory structure mirrors route groups

6. Reliability (MEDIUM)

• rel-no-wait-for-timeout - Never use arbitrary waitForTimeout

Essential Patterns

Locator Priority

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// 1st: Role (best — mirrors accessibility)
page.getByRole('button', { name: 'Submit' })
page.getByRole('tab', { name: 'Network' })
page.getByRole('heading', { name: 'Dashboard' })

// 2nd: Label (for form fields)
page.getByLabel('Email')

// 3rd: Text (for static content, use exact when ambiguous)
page.getByText('Welcome', { exact: true })

// 4th: ID (for inputs without proper labels)
page.locator('#password')

// Last resort: CSS selector
page.locator('button.submit-btn')

Auth Setup Pattern

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// Setup project logs in once per role, all tests reuse the state
// 3 logins for 90+ tests (not 90 logins)

// In test files:
test.use({ role: 'customer' });
test('shows dashboard', async ({ authedPage: page }) => {
    await page.goto('/dashboard');
    await expect(page.getByRole('heading', { level: 1 })).toBeVisible();
});

React Date Input Gotcha

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// fill() doesn't trigger React onChange for date/time inputs
// Use keyboard.type() instead:
await dateInput.click();
await page.keyboard.type('16042026');  // DDMMYYYY

await timeInput.click();
await page.keyboard.type('1000AM');    // 10:00 AM

Strict Mode Fix

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// Bad: matches "Verified" AND "Unverified"
page.getByRole('button', { name: 'Verified' })

// Good: exact match
page.getByRole('button', { name: 'Verified', exact: true })

// Bad: matches heading AND breadcrumb
page.getByText('POS Demo')

// Good: use role to disambiguate
page.getByRole('heading', { name: 'POS Demo' })

Parallelism Decision

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// Default Playwright: fullyParallel: true
// Use this when: tests are independent, each test creates its own data

// Override to sequential: workers: 1
// Use this when: tests share a seeded database with mutable state
// Without this, one test's buy transaction changes the balance another test expects

Configuration Template

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import { defineConfig, devices } from '@playwright/test';

export default defineConfig({
    testDir: './specs',
    fullyParallel: false,              // true if tests are independent
    workers: 1,                        // increase if no shared mutable state
    forbidOnly: !!process.env.CI,
    retries: process.env.CI ? 2 : 0,
    reporter: [['html', { open: 'never' }], ['list']],
    use: {
        baseURL: process.env.PLAYWRIGHT_BASE_URL || 'http://localhost:8000',
        trace: 'on-first-retry',
        screenshot: 'only-on-failure',
        video: 'retain-on-failure',
    },
    projects: [
        { name: 'auth-setup', testMatch: /auth\.setup\.js$/, testDir: './auth' },
        { name: 'chrome', use: { ...devices['Desktop Chrome'] }, dependencies: ['auth-setup'] },
        { name: 'mobile', use: { ...devices['iPhone 14'] }, dependencies: ['auth-setup'], testMatch: /responsive/ },
    ],
});

References

• Playwright Documentation
• Best Practices
• Locators Guide
• Authentication Guide
• Test Assertions
• Auto-waiting

Full Compiled Document

For the complete guide with all rules expanded: AGENTS.md