Chrome extensions

Introduction

note

Extensions only work in Chrome / Chromium launched with a persistent context. Use custom browser args at your own risk, as some of them may break Playwright functionality.

The snippet below retrieves the background page of a Manifest v2 extension whose source is located in ./my-extension.

Note the use of the chromium channel that allows to run extensions in headless mode. Alternatively, you can launch the browser in headed mode.

Sync
Async

from playwright.sync_api import sync_playwright, Playwright

path_to_extension = "./my-extension"
user_data_dir = "/tmp/test-user-data-dir"


def run(playwright: Playwright):
    context = playwright.chromium.launch_persistent_context(
        user_data_dir,
        channel="chromium",
        args=[
            f"--disable-extensions-except={path_to_extension}",
            f"--load-extension={path_to_extension}",
        ],
    )
    if len(context.background_pages) == 0:
        background_page = context.wait_for_event('backgroundpage')
    else:
        background_page = context.background_pages[0]

    # Test the background page as you would any other page.
    context.close()


with sync_playwright() as playwright:
    run(playwright)

import asyncio
from playwright.async_api import async_playwright, Playwright

path_to_extension = "./my-extension"
user_data_dir = "/tmp/test-user-data-dir"


async def run(playwright: Playwright):
    context = await playwright.chromium.launch_persistent_context(
        user_data_dir,
        channel="chromium",
        args=[
            f"--disable-extensions-except={path_to_extension}",
            f"--load-extension={path_to_extension}",
        ],
    )

    if len(context.background_pages) == 0:
        background_page = await context.wait_for_event('backgroundpage')
    else:
        background_page = context.background_pages[0]

    # Test the background page as you would any other page.
    await context.close()


async def main():
    async with async_playwright() as playwright:
        await run(playwright)


asyncio.run(main())

Testing

To have the extension loaded when running tests you can use a test fixture to set the context. You can also dynamically retrieve the extension id and use it to load and test the popup page for example.

Note the use of the chromium channel that allows to run extensions in headless mode. Alternatively, you can launch the browser in headed mode.

First, add fixtures that will load the extension:

conftest.py
from typing import Generator
from pathlib import Path
from playwright.sync_api import Playwright, BrowserContext
import pytest


@pytest.fixture()
def context(playwright: Playwright) -> Generator[BrowserContext, None, None]:
    path_to_extension = Path(__file__).parent.joinpath("my-extension")
    context = playwright.chromium.launch_persistent_context(
        "",
        channel="chromium",
        args=[
            f"--disable-extensions-except={path_to_extension}",
            f"--load-extension={path_to_extension}",
        ],
    )
    yield context
    context.close()


@pytest.fixture()
def extension_id(context) -> Generator[str, None, None]:
    # for manifest v2:
    # background = context.background_pages[0]
    # if not background:
    #     background = context.wait_for_event("backgroundpage")

    # for manifest v3:
    background = context.service_workers[0]
    if not background:
        background = context.wait_for_event("serviceworker")

    extension_id = background.url.split("/")[2]
    yield extension_id

Then use these fixtures in a test:

test_foo.py
from playwright.sync_api import expect, Page


def test_example_test(page: Page) -> None:
    page.goto("https://example.com")
    expect(page.locator("body")).to_contain_text("Changed by my-extension")


def test_popup_page(page: Page, extension_id: str) -> None:
    page.goto(f"chrome-extension://{extension_id}/popup.html")
    expect(page.locator("body")).to_have_text("my-extension popup")

Introduction​

Testing​

Introduction

Testing