def test_firefox_create_instance_with_extension(request, browser, app_url):
    """Test: Load an extension via selenium.

    The dummy extension should add a red border to any web page.
    """
    browser.visit(app_url)

    elem = browser.find_by_css("body")
    elem.is_visible(wait_time=20)

    style = elem._element.get_attribute("style")
    assert "border: 5px solid red;" == style
Test: Load an extension via selenium.

    The dummy extension should add a red border to any web page.
    
tests/tests_firefox_webdriver/test_firefox_extension.py