Handling Authentication and Session Cookies in Playwright

Web automation has evolved, and testing frameworks like Playwright make it easier than ever to simulate real-world user interactions. However, handling authentication and session cookies is often a challenging part of the testing process, especially for dynamic, multi-user applications. In this article, we’ll cover how to manage authentication and session cookies efficiently when using Playwright, ensuring your tests run smoothly while mimicking real user behaviors.

Understanding Authentication and Session Cookies

Authentication refers to the process by which an application verifies a user’s identity. This typically involves logging in with a username and password or using token-based systems like OAuth. Once authenticated, session cookies are used to store user-specific data (such as login status) that allows the user to interact with a site without constantly re-authenticating.

When testing, especially for applications that involve complex user roles or multi-step processes, handling these cookies correctly is essential. In Playwright, session cookies can be captured, stored, and re-used in different tests, which improves test efficiency.

Step-by-Step: Capturing and Using Session Cookies in Playwright

Let’s walk through how you can capture session cookies after a user logs in, then reuse them in subsequent tests without requiring the login process each time. This method helps reduce the overhead of redundant authentication steps, making your tests faster and more streamlined.

1. Setting Up Playwright

Before diving into the code, ensure you have Playwright installed and configured in your project. You can set up Playwright with the following command:

npm install --save-dev playwright

Once Playwright is installed, you can begin writing tests that capture and use session cookies.

2. Capturing Authentication Cookies

To capture cookies, you first need to perform the login process and then save the cookies for reuse. Here’s an example:

const { chromium } = require('playwright');

(async () => {
    const browser = await chromium.launch();
    const context = await browser.newContext();
    const page = await context.newPage();

    // Go to the login page
    await page.goto('https://example.com/login');

    // Perform login
    await page.fill('#username', 'testuser');
    await page.fill('#password', 'password123');
    await page.click('button#login');

    // Wait for navigation after login
    await page.waitForNavigation();

    // Capture and save session cookies
    const cookies = await context.cookies();
    console.log(cookies);

    await browser.close();
})();
        

In this example, the login credentials are entered into the form, and Playwright waits for navigation after successful login. Once logged in, the cookies are captured using context.cookies(), which stores them in memory for later use.

3. Reusing Cookies for Future Sessions

Once you’ve captured the session cookies, you can reuse them in future tests by setting them in a new browser context. Here’s how you can use stored cookies to bypass the login process:

const { chromium } = require('playwright');

(async () => {
    const browser = await chromium.launch();
    const context = await browser.newContext();

    // Set cookies
    await context.addCookies([
        {
            name: 'session_id',
            value: 'your-session-cookie-value',
            domain: 'example.com',
            path: '/'
        }
    ]);

    const page = await context.newPage();
    await page.goto('https://example.com/dashboard');

    // Check if user is still logged in
    await page.waitForSelector('#welcome-message');

    await browser.close();
})();
        

By adding cookies directly to the context, you can navigate to any page in the application as if the user is already logged in, saving time on repeated authentication steps during testing.

Automating Authentication with API Tokens

In some cases, web applications use API tokens instead of traditional session cookies for authentication. Playwright allows you to handle these tokens with ease. Here’s how to set up a Playwright test that works with an API token:

const { chromium } = require('playwright');

(async () => {
    const browser = await chromium.launch();
    const context = await browser.newContext();

    // Set API token in headers
    await context.setExtraHTTPHeaders({
        'Authorization': 'Bearer your-api-token-here'
    });

    const page = await context.newPage();
    await page.goto('https://example.com/dashboard');

    // Check if API-based auth is successful
    await page.waitForSelector('#welcome-message');

    await browser.close();
})();
        

This method involves sending an API token in the HTTP headers with every request, which is commonly used for authentication in modern web applications. Playwright allows you to automate this process, ensuring your tests cover both cookie-based and token-based authentication methods.

Handling Multi-Factor Authentication (MFA)

Many web applications implement Multi-Factor Authentication (MFA) as an added layer of security. Testing MFA flows can be tricky but is crucial for security testing. Playwright can handle MFA by interacting with the second step of the authentication process (such as inputting a code from an email or SMS).

For example, if the second factor involves entering a one-time password (OTP), Playwright can input this code in the following manner:

const otpCode = '123456'; // This would be fetched dynamically in real-world scenarios

await page.fill('#otp', otpCode);
await page.click('button#verify');
        

While handling MFA testing is more complex, integrating it into your Playwright workflow ensures your tests are comprehensive and secure.

Best Practices for Handling Authentication in Playwright

• Re-use Authentication Cookies: Save cookies after login to reuse them in multiple tests, minimizing redundant steps and speeding up test execution.
• Automate Token-Based Authentication: Use Playwright’s ability to send tokens in headers to streamline testing for modern applications.
• Test MFA Thoroughly: Ensure that multi-factor authentication is thoroughly tested by automating the input of OTPs or verification codes.
• Monitor Session Expiry: Verify how the application behaves when session cookies or tokens expire, ensuring that users are prompted to re-authenticate as expected.

Conclusion

Handling authentication and session cookies in Playwright may seem complex at first, but with the right approach, it can be streamlined for efficiency. By capturing and reusing cookies, handling API tokens, and automating complex flows like MFA, Playwright makes it possible to simulate real-world user scenarios with ease.

With these best practices, you can ensure your tests are both robust and efficient, covering all aspects of user authentication and session management in your web applications.