Welcome to the next phase of our course, where we delve into handling asynchronous operations and waiting strategies using Playwright. As web applications become more interactive and dynamic, managing asynchronous events is crucial for ensuring that your automated tests are both reliable and effective. This lesson will guide you through essential techniques for handling asynchronous operations, building on your existing Playwright skills.
Until now, we assumed that the operations that we perform (click, text filling, etc) are completed immediately. But in real world, it's usually not the case. You might say, well, we do await page.click(selector), so we wait for it to complete. But, in fact, when you click a button using Playwright and use await to wait for that action, the promise resolves immediately after the click action is dispatched, not when the onClick method completes. What does this mean?
Let's consider an example when we click on the Load More button in the app that we have investigated in this course. You may have noticed that it does not load everything immediately. It is a beautiful simulation of how things happen in real-world apps. Usually, to receive the data about books, it sends some request to a database, and it takes time to fetch the data from it. What happens in our code when we click it programmatically, is the program proceeds to the next line until the load more button finishes its job. So if we expect the number of visible books to be increased, it may not be the case if the app doesn't update data immediately.
In this lesson, you will learn how to manage asynchronous operations using Playwright's waiting strategies. This will allow your tests to synchronize actions with the web page's state, ensuring that elements are ready for interaction. Let's look at an example:
In this test, we perform the following actions:
-
Page Navigation: The test begins by navigating to the desired URL using
await page.goto('http://localhost:3000'). This ensures we are starting with a fresh state on the target page. -
Using Selectors and Asynchronous Interactions: We interact with the "Load more" button using and then wait for the text 'Load More' to reappear on the page with . After ensuring the text has appeared, we validate the number of elements loaded using and then assert the count with . This ensures that the asynchronous loading of content is successfully completed.
When using waitForSelector, Playwright provides options such as timeout and state to give you more control over waiting for elements on the page. Here's how you can use them:
Timeout
The timeout option allows you to specify how long to wait for the selector to appear before throwing an error. The default timeout is 30 seconds, but you can adjust this to suit your test's specific needs:
State
The state option allows you to define the element's state for which you are waiting. Common states include:
'attached': Ensures the element is present in the DOM.'detached': Ensures the element is not present in the DOM.'visible': Ensures the element is visible.'hidden': Ensures the element is either detached from the DOM or hidden.
Using these options effectively can help tailor your waiting strategies to the specific requirements of your test scenarios, making them more robust and reliable.
Understanding how to handle asynchronous operations is vital as web applications become increasingly dynamic. By mastering waiting strategies, you ensure that your automated tests are synchronized with the web page's behavior, leading to more reliable and accurate results. This skill will not only improve the robustness of your test scripts but also enhance your ability to tackle complex web interactions with confidence.
Feeling ready to tackle some practice tasks? Let's get started on honing these skills further with interactive exercises!
