Testing is one of the most important parts of building full stack applications. It helps make sure your app works correctly and keeps working after updates. In simple terms, testing helps catch bugs before your users see them.
There are many types of testing unit tests, integration tests, and end-to-end (E2E) tests. In this blog, we will focus on E2E testing using Playwright and Cypress. These tools help you test your full stack applications automatically by simulating real user actions like clicking buttons, filling forms, and navigating pages.
If you’re enrolled in a full stack course, learning these tools will help you build better, bug-free applications and become a more confident developer.
What Is End-to-End (E2E) Testing?
End-to-end testing means testing your entire app from the user’s point of view. It checks if all parts of the app (front end, back end, database, etc.) work together correctly.
For example, in a login feature, an E2E test will:
- Open the login page
- Fill in the email and password
- Click the login button
- Check if the user is redirected to the dashboard
This type of testing is very useful in full stack projects where many parts of the app work together.
Why Automate Testing?
Manual testing takes time. You need to check everything again and again every time you make a change.
With automation, your tests run by themselves. This saves time, finds bugs early, and gives you confidence to release updates quickly.
Benefits of automated testing:
- Fast and repeatable
- Reduces human error
- Helps in Continuous Integration (CI)
- Improves code quality
These practices are often part of real-world projects in developer classes.
What Is Playwright?
Playwright is an open-source testing tool built by Microsoft. It can test web apps in all modern browsers like Chrome, Firefox, and Safari.
Playwright lets you:
- Write simple test scripts
- Run tests in multiple browsers
- Interact with web pages like a user
- Test front-end and back-end responses
Playwright supports JavaScript, TypeScript, Python, and more.
What Is Cypress?
Cypress is another popular tool for E2E testing. It runs in the browser and gives fast, real-time feedback. It is great for testing front-end applications, especially if you use frameworks like React or Angular.
Cypress is easy to set up, beginner-friendly, and perfect for small to medium full stack apps.
Installing Playwright
You can start using Playwright in just a few steps.
Step 1: Create a new Node.js project
mkdir my-app-tests
cd my-app-tests
npm init -y
Step 2: Install Playwright
npm install -D playwright
Step 3: Create a test file
// login.test.js
const { test, expect } = require(‘@playwright/test’);
test(‘login test’, async ({ page }) => {
await page.goto(‘http://localhost:3000/login’);
await page.fill(‘input[name=”email”]’, ‘test@example.com’);
await page.fill(‘input[name=”password”]’, ‘password123’);
await page.click(‘button[type=”submit”]’);
await expect(page).toHaveURL(‘http://localhost:3000/dashboard’);
});
Step 4: Run the test
npx playwright test
Playwright will open a browser, perform the steps, and show you the result. You can also run it in headless mode, where the browser runs in the background.
This kind of setup is often done in advanced stages of a full stack course to teach real-time testing.
Installing Cypress
Cypress is also very simple to start.
Step 1: Install Cypress
npm install cypress –save-dev
Step 2: Open Cypress
npx cypress open
This opens the Cypress test runner, where you can create and run tests.
Step 3: Write a test
// cypress/e2e/login.spec.js
describe(‘Login Test’, () => {
it(‘logs in successfully’, () => {
cy.visit(‘http://localhost:3000/login’);
cy.get(‘input[name=”email”]’).type(‘test@example.com’);
cy.get(‘input[name=”password”]’).type(‘password123’);
cy.get(‘button[type=”submit”]’).click();
cy.url().should(‘include’, ‘/dashboard’);
});
});
Step 4: Run the test
From the test runner, click the test file and watch it run in the browser.
Cypress shows each step visually, which helps beginners understand how the test works. That’s why it’s commonly used in developer classes.
Testing the Full Stack
In full stack apps, testing just the front end is not enough. You should also check if the back end is working. Playwright and Cypress can help test:
- API responses
- Server status
- Authentication flows
- Form submissions
Example: Testing API in Cypress
cy.request(‘POST’, ‘/api/login’, {
email: ‘test@example.com’,
password: ‘password123’
}).then((response) => {
expect(response.status).to.eq(200);
});
This sends a request to the back-end API and checks if the response is correct.
Example: Mocking API in Playwright
Playwright allows you to mock API responses during testing.
await page.route(‘**/api/login’, route =>
route.fulfill({
status: 200,
body: JSON.stringify({ message: ‘Login successful’ })
})
);
This is useful when your back end is not ready, or when you want to test specific scenarios.
Best Practices for Automated Testing
1. Use Test IDs
Add data-testid attributes to your HTML elements. This makes your tests more stable and less likely to break when the UI changes.
<input data-testid=”email-input” />
Then in your test:
cy.get(‘[data-testid=email-input]’).type(‘test@example.com’);
2. Keep Tests Independent
Each test should run on its own. Don’t depend on previous tests to create data. Use a clean test environment or reset the database if needed.
3. Use CI Tools
Connect your tests to GitHub Actions, GitLab CI, or Jenkins. This way, your tests run automatically every time you push code.
This process is part of Continuous Integration (CI) and is commonly used in industry projects taught in a full stack course.
4. Test Critical Paths First
Start by testing the most important user actions, such as:
- Login
- Signup
- Create new record
- Update or delete data
Later, add more tests for edge cases and small features.
5. Don’t Over-Test
Automate the most important paths. Some UI features (like colors or layout) may not need E2E tests. Focus on what matters most to your users.
Playwright vs Cypress: Which One to Choose?
Both tools are great. Here’s a quick comparison:
| Feature | Playwright | Cypress |
| Browser support | Chrome, Firefox, Safari | Chrome (best), others in beta |
| Speed | Fast | Very fast |
| Real-time display | No (uses logs) | Yes (visual UI) |
| API testing | Yes | Yes |
| Best for | Cross-browser testing | Easy UI testing |
Use Playwright if you need to test across multiple browsers.
Use Cypress if you want easy setup and a strong visual experience.
Many developers start with Cypress and later explore Playwright in bigger projects. Both are useful skills for students in full stack developer classes.
Final Thoughts
Automated testing makes your full stack apps more stable, reliable, and easy to maintain. Playwright and Cypress are powerful tools that help you test your app like a real user would.
In this blog, you learned:
- What E2E testing is
- How Playwright and Cypress work
- How to write and run tests
- Best practices for automation
- When to use each tool
If you’re serious about building high-quality apps, include testing in your workflow. By taking a full stack course, make testing a part of every project. Start simple, practice regularly, and build strong habits that will help you in every job or project you take on.
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