One time authentication in Playwright gives: browser.newContext: Cookie should have a valid expires, only -1 or a positive number ... is allowed

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05-10-2024

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Playwright's "Cookie Should Have a Valid Expires" Error: A Guide to One-Time Authentication

Navigating the world of automated browser testing often throws up unexpected hurdles. One such roadblock, frequently encountered when working with Playwright and one-time authentication, is the error "browser.newContext: Cookie should have a valid expires, only -1 or a positive number is allowed". This article aims to demystify this error, provide practical solutions, and empower you to overcome this challenge in your testing journey.

The Scenario:

Imagine you're testing an application that requires one-time authentication, perhaps using a login flow with an OTP (One-Time Password). You might be attempting to automate this process by setting a cookie manually to simulate a logged-in state. However, when you run your Playwright script, you encounter the "Cookie should have a valid expires" error.

Example Code:

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

async function login() {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();
  await page.goto('https://example.com/login');

  // Attempting to set a cookie with an invalid expires value
  await page.context().addCookies([
    { name: 'auth_token', value: 'your_token', expires: 'invalid_date' } 
  ]);

  // ...continue with testing
}

login();

The Root of the Problem:

The core issue arises from Playwright's requirement for a valid expires value when setting cookies. The expires attribute should be either -1 (indicating a session cookie that expires when the browser closes) or a positive number representing the number of seconds until the cookie expires. The error message highlights that Playwright doesn't accept arbitrary string values for expires.

Solutions and Strategies:

1. Use a Valid expires Value: Instead of passing an invalid date string, provide a valid numerical value for the expires attribute. If you want the cookie to persist across sessions, choose a large enough positive number (e.g., 3600 * 24 * 365 for a year).
2. Employ Session Cookies: For scenarios where the authentication cookie is valid only for the current session, set expires to -1. This ensures the cookie is automatically deleted when the browser closes.
3. Leverage Playwright's StorageState Feature: A more robust approach is to use Playwright's StorageState functionality. This lets you capture and restore the complete browsing context (including cookies) between different test runs. To utilize this:
   • Record the state: During your initial login, save the browser context using context.storageState({ path: 'path/to/state.json' }).
   • Restore the state: In subsequent test runs, load the stored state using browser.newContext({ storageState: 'path/to/state.json' }).

Code Example with StorageState:

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

async function login() {
  const browser = await chromium.launch({ headless: false });
  const page = await browser.newPage();
  await page.goto('https://example.com/login');

  // Login flow (not shown for brevity)

  // Capture storage state (including cookies)
  await page.context().storageState({ path: 'authState.json' });

  await browser.close();
}

async function runTest() {
  const browser = await chromium.launch({ headless: false });

  // Restore storage state (including authentication cookie)
  const context = await browser.newContext({ storageState: 'authState.json' });
  const page = await context.newPage();

  // Continue with your tests
  await page.goto('https://example.com/protected');

  await browser.close();
}

login();
runTest();

Additional Considerations:

• Cookie Management: Be mindful of cookie domains and paths to ensure proper cookie behavior.
• Security: When handling authentication cookies, prioritize security. Avoid storing them directly in your code.
• HTTP/HTTPS: Ensure the website you're testing is using HTTPS, as insecure connections can lead to cookie security vulnerabilities.

Conclusion:

The "Cookie should have a valid expires" error is a common Playwright obstacle, particularly when dealing with one-time authentication. By understanding the root cause, employing the right techniques, and following security best practices, you can confidently navigate this challenge and ensure successful automated testing.