Keeping Your Playwright Tests Clean: Session Management 101
Playwright is a powerful tool for browser automation, but maintaining a clean environment for your tests is crucial for reliable results. One common issue arises when browser sessions persist across test executions, leading to unexpected behavior and data contamination. This article will delve into the "How to clean browser session between executions in Playwright" problem and provide practical solutions.
The Problem: Dirty Sessions and Their Consequences
Imagine you're testing an e-commerce website. In your first test, you add an item to the cart. If you don't clear the browser session, the cart will still contain the item when you run your next test, potentially affecting the outcome. This is just one example of how a dirty session can lead to unpredictable and inaccurate test results.
Sample Code with Session Persistence Issue
const { chromium } = require('playwright');
async function test1() {
const browser = await chromium.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com/');
// Add item to cart
await page.click('button[data-testid="add-to-cart"]');
await browser.close();
}
async function test2() {
const browser = await chromium.launch();
const page = await browser.newPage();
await page.goto('https://www.example.com/');
// Expect cart to be empty, but it's not!
await page.waitForSelector('button[data-testid="cart-empty"]');
await browser.close();
}
test1();
test2();
In this example, test2 fails because the cart remains populated from the previous execution of test1.
Solutions: Ensuring a Clean Slate
Here are the key strategies to ensure a clean browser session for each test execution:
-
Close Browser Instance After Each Test: The simplest solution is to close the browser instance after each test. This guarantees a fresh browser environment for every execution.
async function test1() { const browser = await chromium.launch(); const page = await browser.newPage(); await page.goto('https://www.example.com/'); await page.click('button[data-testid="add-to-cart"]'); await browser.close(); // Close browser after test } async function test2() { const browser = await chromium.launch(); const page = await browser.newPage(); await page.goto('https://www.example.com/'); await page.waitForSelector('button[data-testid="cart-empty"]'); // Expect cart to be empty await browser.close(); // Close browser after test } -
Context Isolation: Playwright offers "contexts" - separate environments within a browser instance. Creating a new context for each test effectively isolates the browser state.
const { chromium } = require('playwright'); async function test1() { const browser = await chromium.launch(); const context = await browser.newContext(); const page = await context.newPage(); await page.goto('https://www.example.com/'); await page.click('button[data-testid="add-to-cart"]'); await browser.close(); } async function test2() { const browser = await chromium.launch(); const context = await browser.newContext(); // Create new context const page = await context.newPage(); await page.goto('https://www.example.com/'); await page.waitForSelector('button[data-testid="cart-empty"]'); // Expect cart to be empty await browser.close(); } -
Browser Persistence (with Caution): While not recommended for general testing, you can retain the browser instance between tests if you need to keep certain settings, extensions, or login states. However, this requires careful management to prevent state leakage between tests. Ensure you clear any relevant data (cookies, localStorage, etc.) before starting each test.
const { chromium } = require('playwright'); let browser; async function test1() { if (!browser) { browser = await chromium.launch(); } const page = await browser.newPage(); await page.goto('https://www.example.com/'); await page.click('button[data-testid="add-to-cart"]'); } async function test2() { if (!browser) { browser = await chromium.launch(); } const page = await browser.newPage(); await page.goto('https://www.example.com/'); // Clear cart data before starting the test await page.evaluate(() => { localStorage.clear(); // Clear local storage document.cookie = ""; // Clear cookies }); await page.waitForSelector('button[data-testid="cart-empty"]'); // Expect cart to be empty }
Choosing the Right Approach
The best approach depends on your specific needs:
- For most scenarios, closing the browser instance after each test is the most straightforward and reliable solution.
- If you require browser-level settings or extensions to persist, using contexts is a good alternative.
- Browser persistence is suitable for situations where you need to maintain specific states, but requires careful implementation to avoid data contamination.
Remember to prioritize clean sessions for reliable and accurate test results. Choose the approach that best suits your testing requirements and ensure your tests are running in a clean and predictable environment.
Additional Resources
- Playwright Documentation: https://playwright.dev/docs/
- Playwright Examples: https://github.com/microsoft/playwright-examples
By following these best practices and understanding the nuances of session management, you can ensure that your Playwright tests provide valuable and accurate feedback about your application's behavior.
