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Storage

Tests often need to start with saved values or check data written by an extension. playwright-webext provides extension.storage to read and write that data directly from your test, without writing service-worker evaluation code for each operation. You can set storage keys before opening a page and check what a UI action saved.

The storage methods mirror the original Chrome Extensions Storage API, using the same arguments and return values with promises. Your extension needs the storage permission.

The examples below use extension.storage.local. You can also use extension.storage.sync and extension.storage.session.

Read from storage​

Read a key with get():

const result = await extension.storage.local.get('key');
// result: { key: 'value' }

get() returns an object containing the requested keys. Omit the argument to read all values.

Write to storage​

Write a key with set():

await extension.storage.local.set({ key: 'value' });

Assert stored values​

Use expect(key) to check a saved value. Assertions retry while your extension writes asynchronously and support Playwright matchers, including .not:

await extension.storage.local.expect('saved').toEqual(true);
await extension.storage.local.expect('theme').not.toEqual('light');

Omit the key or pass undefined to check the whole storage area:

await extension.storage.local.expect().toEqual({ saved: true, theme: 'dark' });

Example​

Set storage keys before opening an extension page to test how it displays saved values. This example assumes your options page reads theme from local storage and displays it in a “Theme” select. If your extension initializes storage asynchronously, wait for that initialization before seeding values so it cannot overwrite them.

test/storage.spec.ts
import { expect } from '@playwright/test';
import { test } from 'playwright-webext';

test('displays the saved theme', async ({ extension }) => {
  await extension.storage.local.set({ theme: 'dark' });

  const optionsPage = await extension.openOptions();
  await expect(optionsPage.getByLabel('Theme')).toHaveValue('dark');
});

See the Options page guide for checking storage after a UI action, and the ExtensionStorage API for all available methods and storage areas.