Test Automation — E2E, API, Contract Testing

E2E Testing Tools

Tool	Strength
Selenium	Multi-language, mature
Cypress	Great DX, in-browser
Playwright ⭐	Multi-browser, fast, Microsoft
Puppeteer	Chromium only
TestCafe	No WebDriver

Playwright Example

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

test('login flow', async ({ page }) => {
  await page.goto('https://app.com/login');
  await page.fill('#email', 'rahim@x.com');
  await page.fill('#password', 'secret');
  await page.click('button[type=submit]');
  await expect(page).toHaveURL(/dashboard/);
  await expect(page.locator('h1')).toHaveText('Welcome');
});

Cypress Example

describe('Login', () => {
  it('should login', () => {
    cy.visit('/login');
    cy.get('#email').type('rahim@x.com');
    cy.get('#password').type('secret');
    cy.get('button').click();
    cy.url().should('include', '/dashboard');
  });
});

Page Object Pattern ⭐

// LoginPage.ts
class LoginPage {
  constructor(page) { this.page = page; }
  async goto() { await this.page.goto('/login'); }
  async login(email, pass) {
    await this.page.fill('#email', email);
    await this.page.fill('#password', pass);
    await this.page.click('button[type=submit]');
  }
}
// Usage: tests become readable, selectors centralized

API Testing

// Postman Collection + Newman CLI
newman run api-tests.json

// REST Assured (Java)
given().contentType("application/json").body(user)
.when().post("/api/users")
.then().statusCode(201).body("id", notNullValue());

// Supertest (Node)
const res = await request(app).post('/api/users').send({email});
expect(res.status).toBe(201);

Contract Testing ⭐

Consumer-provider API contract validate — breaking change early detect।

// Pact — Consumer writes expectation
await provider.addInteraction({
  state: 'user exists',
  uponReceiving: 'GET /users/1',
  willRespondWith: { status: 200, body: { id: 1, name: "Rahim" } }
});

// Provider verifies
pact-provider-verifier --provider-base-url=http://localhost:3000

Visual Regression

Screenshot compare — unintended UI change catch।

Tools: Percy, Chromatic, Playwright screenshots, BackstopJS।

Mobile Testing

Appium (native), Detox (React Native), Espresso (Android), XCUITest (iOS)।

Accessibility Testing

// Playwright + axe-core
import AxeBuilder from '@axe-core/playwright';
const results = await new AxeBuilder({ page }).analyze();
expect(results.violations).toEqual([]);

Test Data Management

• Factories (faker, bogus)
• Fixtures (JSON seed)
• Database reset per test
• Docker compose for DB
• Test containers (disposable)

Flaky Tests ⭐

Sometimes pass, sometimes fail। Common causes:

• Timing (hardcoded sleep)
• Shared state
• External dependency
• Async race condition
• Test order dependency

Fixes

• Explicit waits (not sleep)
• Isolation per test
• Retry mechanism (last resort)
• Quarantine flaky → fix first

CI Integration

# GitHub Actions
- run: npm test
- run: npx playwright test
- uses: actions/upload-artifact@v4
  if: always()
  with:
    name: test-results
    path: test-results/