PageObjectModel Playwright, execute the locator().all() function - 'The execution context has been terminated, possibly due to navigating to another...'

Question

PageObjectModel Playwright, execute the locator().all() function - 'The execution context has been terminated, possibly due to navigating to another...'

Hey there, I'm currently working on a basic test using POM.

Here is a snippet from one of my PageObjects Class:

import { Expect, Page, Locator } from "@playwright/test";

export class InventoryPage {
  readonly page: Page;
  readonly addToCartBtn: Locator;
  readonly addToCartBtnAll: Promise<Array<Locator>>;
  readonly cartIcon: Locator;

  constructor(page: Page) {
    this.page = page;
    this.addToCartBtn = page.locator("button.btn_inventory");
    this.addToCartBtnAll = page.locator("button.btn_inventory").all();
    this.cartIcon = page.locator(".shopping_cart_badge");
  }

  async addAllItemsToCart() {
    for (let item of await this.addToCartBtnAll) await item.click();
  }

  async addRandomItemToCart() {
    await this.addToCartBtn
      .nth(Math.floor(Math.random() * (await this.addToCartBtnAll).length))
      .click();
  }
}

The issue arises with the following lines:

readonly addToCartBtnAll: Promise<Array<Locator>>;
this.addToCartBtnAll = page.locator("button.btn_inventory").all();

Whenever I create an instance of this class within a test in the beforeEach hook, the test fails prior to execution...

Error: locator.all: Execution context was destroyed, most likely because of a navigation
    at InventoryPage

Does anyone have any insights into what might be causing this issue with the locator().all() function in the page object?

I've managed to find a workaround for now by avoiding the

Promise<Array<Locator>>

type and using .all() elsewhere in the code, but I am still curious as to why Playwright seems to have trouble with this specific type in constructors...

typescript testing automated-tests playwright playwright-test

Answer 1

Answer №1

.all() is a function in Playwright that triggers browser automation actions. All actions must be awaited as they involve communicating with a separate process, the browser, which takes time to complete.

If you define a locator but don't perform any action on it, the browser remains inactive. In this case, there's no need to await the code.

It's important to note that constructors in programming do not work asynchronously; they return an object immediately without using promises for network or system APIs. As such, asynchronous behavior should be kept separate from constructor methods.

The Page Object Model (POM) approach involves defining locators synchronously in the constructor and providing high-level action methods that utilize these locators for various actions and assertions.

One of the key methods in POM should be goto, which sets up the page initially by calling page.goto along with any additional necessary steps.

In your code example, having separate locators like:

this.addToCartBtn = page.locator("button.btn_inventory");
this.addToCartBtnAll = page.locator("button.btn_inventory").all();

is unnecessary. Instead, you can simply use:

this.addToCartBtn = page.locator("button.btn_inventory");

Since locators are re-evaluated during each action call, this single locator works for both singular and plural contexts. However, it's advisable to use a more precise selector when running in strict mode to avoid using discouraged actions like .first(), .last(), or nth().

To address your error situation, ensure that your test case follows the standard POM pattern where goto is called after instantiation instead of concurrently with the .all() method:

const inventoryPage = new InventoryPage(page); // initiates .all()
await page.goto(...); // resets context
await inventoryPage.addAllItemsToCart(); // throws error

By adhering to the recommended POM structure, you can prevent unexpected navigation issues caused by async operations conflicting with set-up steps.

Playwright best practices discourage using CSS selectors to target elements since they're not user-facing attributes. It's preferable to select elements based on roles, text content, titles, labels, or values.

Without specific details of your use case, I recommend reviewing your current code to align it with Playwright conventions and avoiding non-deterministic elements in tests to prevent potential debugging challenges arising from intermittent failures.

Answer 2

.all() is a function in Playwright that triggers browser automation actions. All actions must be awaited as they involve communicating with a separate process, the browser, which takes time to complete.

If you define a locator but don't perform any action on it, the browser remains inactive. In this case, there's no need to await the code.

It's important to note that constructors in programming do not work asynchronously; they return an object immediately without using promises for network or system APIs. As such, asynchronous behavior should be kept separate from constructor methods.

The Page Object Model (POM) approach involves defining locators synchronously in the constructor and providing high-level action methods that utilize these locators for various actions and assertions.

One of the key methods in POM should be goto, which sets up the page initially by calling page.goto along with any additional necessary steps.

In your code example, having separate locators like:

this.addToCartBtn = page.locator("button.btn_inventory");
this.addToCartBtnAll = page.locator("button.btn_inventory").all();

is unnecessary. Instead, you can simply use:

this.addToCartBtn = page.locator("button.btn_inventory");

Since locators are re-evaluated during each action call, this single locator works for both singular and plural contexts. However, it's advisable to use a more precise selector when running in strict mode to avoid using discouraged actions like .first(), .last(), or nth().

To address your error situation, ensure that your test case follows the standard POM pattern where goto is called after instantiation instead of concurrently with the .all() method:

const inventoryPage = new InventoryPage(page); // initiates .all()
await page.goto(...); // resets context
await inventoryPage.addAllItemsToCart(); // throws error

By adhering to the recommended POM structure, you can prevent unexpected navigation issues caused by async operations conflicting with set-up steps.

Playwright best practices discourage using CSS selectors to target elements since they're not user-facing attributes. It's preferable to select elements based on roles, text content, titles, labels, or values.

Without specific details of your use case, I recommend reviewing your current code to align it with Playwright conventions and avoiding non-deterministic elements in tests to prevent potential debugging challenges arising from intermittent failures.

PageObjectModel Playwright, execute the locator().all() function - 'The execution context has been terminated, possibly due to navigating to another...'

Answer №1

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