def driver(extra_overlay: AppHarness):
    """Get an instance of the browser open to the extra overlay app.

    Args:
        extra_overlay: harness for the ExtraOverlay app.

    Yields:
        WebDriver instance.
    """
    driver = extra_overlay.frontend()
    try:
        token_input = driver.find_element(By.ID, "token")
        assert token_input
        # wait for the backend connection to send the token
        token = extra_overlay.poll_for_value(token_input)
        assert token is not None

        yield driver
    finally:
        driver.quit()
Get an instance of the browser open to the extra overlay app.

    Args:
        extra_overlay: harness for the ExtraOverlay app.

    Yields:
        WebDriver instance.
    
tests/integration/test_extra_overlay_function.py