Playwright debug test to not close browser

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05-10-2024

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Keep Your Browser Open: Debugging Playwright Tests Without Automatic Closure

Debugging Playwright tests can be a frustrating experience if the browser closes immediately after the test finishes. This makes it impossible to inspect the DOM, analyze network requests, or understand why your test failed. Thankfully, Playwright provides a simple way to keep the browser open after your tests complete, allowing for a more thorough debugging session.

The Problem: A Browser That Vanishes

Imagine this scenario: you've written a Playwright test that interacts with a web application. You run the test, but it fails. You'd love to see what happened in the browser, but unfortunately, it closes immediately, leaving you with nothing but a cryptic error message.

Here's a simple example of a test that closes the browser after execution:

const { test, expect } = require('@playwright/test');

test('My Failing Test', async ({ page }) => {
  await page.goto('https://www.example.com');
  await expect(page.locator('h1')).toBeVisible(); // This line will likely fail
});

This test will navigate to example.com and try to find an <h1> element. If the element is not found, the test will fail and the browser will automatically close.

The Solution: launchPersistentContext to the Rescue

Playwright's launchPersistentContext method allows you to create a persistent browser context, ensuring that the browser stays open even after the test finishes.

Here's how you can modify the code to keep the browser open:

const { test, expect } = require('@playwright/test');

test('My Failing Test', async ({ page }) => {
  await page.goto('https://www.example.com');
  await expect(page.locator('h1')).toBeVisible(); // This line will likely fail
}, {
  persistent: true 
});

By adding persistent: true to the test configuration, the browser will now remain open even after the test completes. You can then interact with the browser using the browser developer tools, examine network requests, or manually test the functionality in question.

Why This Works

launchPersistentContext creates a unique browser context that persists across multiple tests, effectively creating a "shared" browser instance for all tests in the file. This allows you to keep the browser open and observe the effects of your test runs.

Best Practices

• Isolate Your Tests: When using launchPersistentContext, ensure that your tests are isolated from each other. Avoid modifying the browser state in one test that might affect subsequent tests.
• Use headless: false: To easily access the browser visually, use headless: false when launching your browser. This will open a visible browser window for debugging.

Going Further

Playwright offers more sophisticated debugging options:

• Logging: Configure logging to get detailed information about your tests and the browser interactions.
• Tracing: Generate traces to capture detailed information about your tests, including screenshots, network requests, and performance data.
• Code Coverage: Explore Playwright's support for code coverage to identify untested parts of your code.

By mastering the art of debugging Playwright tests, you'll ensure a smoother development process and create robust web applications.