    async def click_start_server(browser, username):
        """start the server for one user via the Start Server button, index = 0 or 1"""
        start_btn_xpath = f'//a[contains(@href, "spawn/{username}")]/preceding-sibling::button[contains(@class, "start-button")]'
        start_btn = browser.locator(start_btn_xpath)
        await expect(start_btn).to_be_enabled()
        await start_btn.click()
start the server for one user via the Start Server button, index = 0 or 1
jupyterhub/tests/browser/test_browser.py