Playwright test with a loop timing out after 30 seconds

by

Summary

The issue at hand is a Playwright test timing out after 30 seconds when attempting to create 40 users in a system using a sequential forEach loop. This approach is not scalable and leads to reliability issues. A better approach is needed to handle bulk user creation in Playwright.

Root Cause

The root cause of this issue is the sequential execution of user creation tasks, which can be time-consuming and prone to timeout errors. The current script uses a forEach loop to create users one by one, resulting in a linear increase in execution time. Key causes include:

  • Sequential execution: Creating users one by one
  • Timeout limits: Playwright’s default timeout is too low for bulk operations
  • Lack of parallelism: Not utilizing multiple browser contexts or workers

Why This Happens in Real Systems

This issue occurs in real systems due to the inherent limitations of sequential execution and the need for scalability. When dealing with large datasets or repetitive actions, parallelism becomes essential to ensure reliability and efficiency. In this case, the system is not designed to handle bulk user creation, leading to timeout errors and reliability issues.

Real-World Impact

The real-world impact of this issue includes:

  • Failed test runs: Timeout errors causing test runs to fail
  • Inconsistent results: Inability to create all 40 users reliably
  • Increased maintenance: Need for frequent test reruns and debugging
  • Scalability limitations: Inability to handle large datasets or repetitive actions

Example or Code

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

test('create users in parallel', async ({ browser }) => {
  const users = Array(40).fill(0).map((_, index) => `user${index}`);
  const browserContexts = await Promise.all(users.map(() => browser.newContext()));
  await Promise.all(users.map((user, index) => {
    const page = browserContexts[index].newPage();
    return page.goto('https://example.com/create-user')
      .then(() => page.fill('input[name="username"]', user))
      .then(() => page.click('button[type="submit"]'));
  }));
});

How Senior Engineers Fix It

Senior engineers fix this issue by utilizing parallelism and optimizing the test script. This includes:

  • Using multiple browser contexts or workers: To create users in parallel
  • Implementing retry mechanisms: To handle occasional failures
  • Optimizing the test script: To reduce execution time and improve reliability
  • Monitoring and logging: To identify and debug issues

Why Juniors Miss It

Juniors may miss this issue due to:

  • Lack of experience: Limited exposure to large-scale testing and parallelism
  • Insufficient knowledge: Unfamiliarity with Playwright’s capabilities and best practices
  • Overemphasis on simplicity: Focusing on simple, sequential solutions rather than scalable, parallel approaches
  • Inadequate testing: Not thoroughly testing the script with large datasets or repetitive actions