E2e Testing

E2E Testing Patterns

Comprehensive Playwright patterns for building stable, fast, and maintainable E2E test suites.

Test File Organization

tests/
├── e2e/
│   ├── auth/
│   │   ├── login.spec.ts
│   │   ├── logout.spec.ts
│   │   └── register.spec.ts
│   ├── features/
│   │   ├── browse.spec.ts
│   │   ├── search.spec.ts
│   │   └── create.spec.ts
│   └── api/
│       └── endpoints.spec.ts
├── fixtures/
│   ├── auth.ts
│   └── data.ts
└── playwright.config.ts

Page Object Model (POM)

import { Page, Locator } from '@playwright/test';

export class ItemsPage {
  readonly page: Page;
  readonly searchInput: Locator;
  readonly itemCards: Locator;
  readonly createButton: Locator;

  constructor(page: Page) {
    this.page = page;
    this.searchInput = page.locator('[data-testid="search-input"]');
    this.itemCards = page.locator('[data-testid="item-card"]');
    this.createButton = page.locator('[data-testid="create-btn"]');
  }

  async goto() {
    await this.page.goto('/items');
    await this.page.waitForLoadState('networkidle');
  }

  async search(query: string) {
    await this.searchInput.fill(query);
    await this.page.waitForResponse((resp) => resp.url().includes('/api/search'));
    await this.page.waitForLoadState('networkidle');
  }

  async getItemCount() {
    return await this.itemCards.count();
  }
}

Test Structure

import { test, expect } from '@playwright/test';
import { ItemsPage } from '../../pages/ItemsPage';

test.describe('Item Search', () => {
  let itemsPage: ItemsPage;

  test.beforeEach(async ({ page }) => {
    itemsPage = new ItemsPage(page);
    await itemsPage.goto();
  });

  test('should search by keyword', async ({ page }) => {
    await itemsPage.search('test');

    const count = await itemsPage.getItemCount();
    expect(count).toBeGreaterThan(0);

    await expect(itemsPage.itemCards.first()).toContainText(/test/i);
    await page.screenshot({ path: 'artifacts/search-results.png' });
  });

  test('should handle no results', async ({ page }) => {
    await itemsPage.search('xyznonexistent123');

    await expect(page.locator('[data-testid="no-results"]')).toBeVisible();
    expect(await itemsPage.getItemCount()).toBe(0);
  });
});

Playwright Configuration

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

export default defineConfig({
  testDir: './tests/e2e',
  fullyParallel: true,
  forbidOnly: !!process.env.CI,
  retries: process.env.CI ? 2 : 0,
  workers: process.env.CI ? 1 : undefined,
  reporter: [
    ['html', { outputFolder: 'playwright-report' }],
    ['junit', { outputFile: 'playwright-results.xml' }],
    ['json', { outputFile: 'playwright-results.json' }],
  ],
  use: {
    baseURL: process.env.BASE_URL || 'http://localhost:3000',
    trace: 'on-first-retry',
    screenshot: 'only-on-failure',
    video: 'retain-on-failure',
    actionTimeout: 10000,
    navigationTimeout: 30000,
  },
  projects: [
    { name: 'chromium', use: { ...devices['Desktop Chrome'] } },
    { name: 'firefox', use: { ...devices['Desktop Firefox'] } },
    { name: 'webkit', use: { ...devices['Desktop Safari'] } },
    { name: 'mobile-chrome', use: { ...devices['Pixel 5'] } },
  ],
  webServer: {
    command: 'npm run dev',
    url: 'http://localhost:3000',
    reuseExistingServer: !process.env.CI,
    timeout: 120000,
  },
});

Flaky Test Patterns

Quarantine

test('flaky: complex search', async ({ page }) => {
  test.fixme(true, 'Flaky - Issue #123');
  // test code...
});

test('conditional skip', async ({ page }) => {
  test.skip(process.env.CI, 'Flaky in CI - Issue #123');
  // test code...
});

Identify Flakiness

npx playwright test tests/search.spec.ts --repeat-each=10
npx playwright test tests/search.spec.ts --retries=3

Common Causes & Fixes

Race conditions:

// Bad: assumes element is ready
await page.click('[data-testid="button"]');

// Good: auto-wait locator
await page.locator('[data-testid="button"]').click();

Network timing:

// Bad: arbitrary timeout
await page.waitForTimeout(5000);

// Good: wait for specific condition
await page.waitForResponse((resp) => resp.url().includes('/api/data'));

Animation timing:

// Bad: click during animation
await page.click('[data-testid="menu-item"]');

// Good: wait for stability
await page.locator('[data-testid="menu-item"]').waitFor({ state: 'visible' });
await page.waitForLoadState('networkidle');
await page.locator('[data-testid="menu-item"]').click();

Artifact Management

Screenshots

await page.screenshot({ path: 'artifacts/after-login.png' });
await page.screenshot({ path: 'artifacts/full-page.png', fullPage: true });
await page.locator('[data-testid="chart"]').screenshot({ path: 'artifacts/chart.png' });

Traces

await browser.startTracing(page, {
  path: 'artifacts/trace.json',
  screenshots: true,
  snapshots: true,
});
// ... test actions ...
await browser.stopTracing();

Video

// In playwright.config.ts
use: {
  video: 'retain-on-failure',
  videosPath: 'artifacts/videos/'
}

CI/CD Integration

# .github/workflows/e2e.yml
name: E2E Tests
on: [push, pull_request]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm ci
      - run: npx playwright install --with-deps
      - run: npx playwright test
        env:
          BASE_URL: ${{ vars.STAGING_URL }}
      - uses: actions/upload-artifact@v4
        if: always()
        with:
          name: playwright-report
          path: playwright-report/
          retention-days: 30

Test Report Template

# E2E Test Report

**Date:** YYYY-MM-DD HH:MM
**Duration:** Xm Ys
**Status:** PASSING / FAILING

## Summary

- Total: X | Passed: Y (Z%) | Failed: A | Flaky: B | Skipped: C

## Failed Tests

### test-name

**File:** `tests/e2e/feature.spec.ts:45`
**Error:** Expected element to be visible
**Screenshot:** artifacts/failed.png
**Recommended Fix:** [description]

## Artifacts

- HTML Report: playwright-report/index.html
- Screenshots: artifacts/\*.png
- Videos: artifacts/videos/\*.webm
- Traces: artifacts/\*.zip

Wallet / Web3 Testing

test('wallet connection', async ({ page, context }) => {
  // Mock wallet provider
  await context.addInitScript(() => {
    window.ethereum = {
      isMetaMask: true,
      request: async ({ method }) => {
        if (method === 'eth_requestAccounts') return ['0x1234567890123456789012345678901234567890'];
        if (method === 'eth_chainId') return '0x1';
      },
    };
  });

  await page.goto('/');
  await page.locator('[data-testid="connect-wallet"]').click();
  await expect(page.locator('[data-testid="wallet-address"]')).toContainText('0x1234');
});

Financial / Critical Flow Testing

test('trade execution', async ({ page }) => {
  // Skip on production — real money
  test.skip(process.env.NODE_ENV === 'production', 'Skip on production');

  await page.goto('/markets/test-market');
  await page.locator('[data-testid="position-yes"]').click();
  await page.locator('[data-testid="trade-amount"]').fill('1.0');

  // Verify preview
  const preview = page.locator('[data-testid="trade-preview"]');
  await expect(preview).toContainText('1.0');

  // Confirm and wait for blockchain
  await page.locator('[data-testid="confirm-trade"]').click();
  await page.waitForResponse((resp) => resp.url().includes('/api/trade') && resp.status() === 200, { timeout: 30000 });

  await expect(page.locator('[data-testid="trade-success"]')).toBeVisible();
});