What are the Causes of ProtocolError in Playwright?

Pragya Yadav

A ProtocolError in Playwright arises when a communication issue exists between Playwright and the browser. The reasons can range from the browser’s internal operations to how Playwright controls or interacts with it. Checking the exact error message will help to get more context regarding the error cause.

This article lists the most common causes of ProtocolError in Playwright, their examples, and how to avoid these errors.

Causes of ProtocolError in Playwright

These are some common causes for getting ProtocolError in Playwright and their examples:

Browser Compatibility Issues

If Playwright is trying to use an API or feature that your current browser version does not support, then you might run into ProtocolError, due to browser incompatibility.

Example: Using Playwright with a version of Chromium that doesn’t support a particular API feature, such as a newer DOM manipulation method.

Websocket Disconnections

Playwright uses WebSocket connections to communicate with the browser. If this connection gets interrupted or disconnected somehow, then it will result in ProtocolError.

Example: The WebSocket connection between Playwright and the browser intermittently closes due to network instability or server issues.

Network Issues

There can be network issues such as firewall restrictions, network outages, proxy rules, etc., which may prevent Playwright from sending commands and receiving responses from the browser.

Example: If your test environment is behind the organization’s proxy, then Playwright’s WebSocket connections to communicate with the browser may get interrupted. This will lead to dropped or failed messages during communication.

Timeouts

When you have slow network connections, heavy resource usage, or unresponsive web pages, then operations may take longer than expected. Such delays or timeouts may result in a ProtocolError.

Example: A page takes too long to load due to server-side issues, and the default timeout for navigation is surpassed.

Concurrent Operations

Sometimes, the test script performs many concurrent actions simultaneously or quickly in sequence without waiting for the previous action to complete. These resource-intensive actions without proper waiting can result in race conditions and, eventually, ProtocolError.

Example: You click a link on the UI and immediately navigate to a new URL without waiting for the click to be fully processed by the browser.

Wrong API Usage

Incorrect API use due to human error or a bug in Playwright may cause ProtocolError.

Example: Playwright tries to interact with a DOM element, which should be rendered. However, due to some timing issues, it is absent.

Browser Crash

If the browser crashes or encounters an internal error, all the subsequent Playwright commands may result in ProtocolError.

Example: The browser instance crashes due to an out-of-memory error while running a heavy test script.

Version Mismatch

If you are using a version of Playwright that is incompatible with the downloaded browser binaries or with your codebase, this mismatch can cause issues.

Example: You have updated Playwright to a new version, but the browser binaries are still from an older version, which leads to incompatibilities and protocol issues.

Resolution of ProtocolError in Playwright

You can use the below tips to avoid ProtocolError in Playwright:

• Use Compatible Browser Version: Browser and Playwright versions should be compatible with each other. Make sure that you update the browser binaries and Playwright version to the latest.

  Example: npm update playwright or npm install playwright@latest

• Maintain a Stable Network Connection: Use a stable network connection for running your tests. Avoid network issues that might disrupt the WebSocket communication between Playwright and the browser.
• Manage Websockets: Though it is generally handled internally by Playwright. However, if you are managing the WebSockets directly in the tests, ensure they remain stable. In case of disconnections, they should be handled gracefully.
• Optimize Test Execution: Manage the test execution in a way that the resources are optimized but not overwhelmed during parallel test execution. Too many simultaneous tests may cause browser crashes or slowness.

  Example: // In playwright.config.js
  module.exports = {
    workers: 4, // Adjust based on system capability
  };

• Use Timeout Management: To manage server and network response times, asynchronous operations, and navigation, use proper waits and timeout management. You can set global and individual timeouts for that purpose.

  Example: // Set a global timeout
  test.setTimeout(10000); // 10 seconds
  
  // Set timeout for specific actions
  await page.waitForSelector(selector, { timeout: 5000 });

• Handle Sequential Operations: Actions that need the previous action to be completed first in sequence should be handled diligently. For example, the test script navigates to a new page after a button click, so there should be a provision to wait for the click to get processed first correctly.

  Example: await page.click('button#submit');
  await page.waitForNavigation();

• Manage Asynchronous Behavior: In JavaScript and TypeScript environments, it is vital to manage the asynchronous behavior to avoid the ProtocolError. You can use async and await for that purpose.

  Example: test('example test', async () => {
    await page.goto('https://example.com');
    // more asynchronous operations
  });

• Avoid Race Conditions: Know potential race conditions in your tests, where one operation might not be complete before the other starts. Use features like waitForSelector or waitForNavigation to avoid these situations.

  Example: const [response] = await Promise.all([
    page.waitForNavigation(),
    page.click('button#link'),
  ]);

• Activate Playwright Headful Mode: Some issues might not be identifiable in Playwright headless mode. Here, activate Playwright in headful mode (with the browser visible) to identify problems.

  Example: const browser = await playwright.chromium.launch({ headless: false });

Apart from these tips, you should also have proper error handling to manage the errors gracefully with appropriate error messages. Additionally, get the test scripts peer-reviewed and have periodic reviews to keep only relevant test scripts. Any deprecated methods should be identified and removed to avoid any compatibility issues.

Using AI to Avoid Playwright Errors

It becomes frustrating for the testing team to resolve the errors related to browser compatibility, network stability, WebSocket issues, race conditions, etc. Frankly, these can be avoided right away. We have many intelligent tools available in the market that do not need so much effort and time to manage such low-level details in test scripts.

testRigor is one of these tools, which works on generative AI to ease the overall testing process. You can create test cases in plain English to test web, mobile (hybrid, native), API, and desktop applications easily without any maintenance nightmares. testRigor has its own locators to identify the elements using the text that is visible on the screen. No more unstable CSS/XPath locators. Not only this, it uses self-healing to incorporate most of the UI and application changes intuitively into the test scripts.

Are you tired of managing the waits and timeouts? Here is the good news: testRigor manages all of this automatically for you. No more deliberate insertions of waits in the test scripts.

Forget browser compatibility issues. You just need to select the browser/platform environment where you want to run your test cases. Also, with the vast integrations, you can easily integrate your test suites with all significant test management, infrastructure providers, CI/CD, CRM, and ERP tools.

Know more about testRigor’s top features.

Conclusion

The bottom line is that better options and alternatives are available, which can save you enormous time, effort, and cost. Why not avail them? These AI-driven solutions are intelligent enough to handle mundane tasks where we should not waste human intelligence and effort.

Use the expertise of your team where the human touch is required, as in exploratory testing or creating more robust test cases to achieve excellent test coverage. Make an informed decision and choose better to save a considerable maintenance and test creation effort through these AI-powered software testing tools.

“We spent so much time on maintenance when using Selenium, and we spend nearly zero time with maintenance using testRigor.”

Keith Powe VP Of Engineering - IDT