WebDriver报错：AttributeError: 'NoneType'对象无get_screenshot_as_file属性

问题根源 #

你的代码中出现AttributeError: 'NoneType' object has no attribute 'get_screenshot_as_file'的核心原因有两个：

• 当setup fixture执行失败（比如浏览器启动失败、指定了不支持的浏览器名称），全局driver会保持初始的None值，此时hook触发截图操作就会调用空对象的方法报错。
• 全局变量的作用域在pytest的hook执行流程中存在不可控性，比如hook执行时机与fixture生命周期不匹配时，driver可能还未完成初始化。

解决方案 #

方案1：从测试实例获取Driver（推荐，无全局变量依赖） #

放弃全局driver，改为从测试用例的类实例中获取setup fixture注入的driver属性，逻辑更健壮，符合pytest的fixture设计规范：

修改pytest_runtest_makereport和_capture_screenshot函数：

@pytest.mark.hookwrapper
def pytest_runtest_makereport(item):
    """
    Extends the PyTest Plugin to take and embed screenshot in html report, whenever test fails.
    :param item:
    """
    pytest_html = item.config.pluginmanager.getplugin('html')
    outcome = yield
    report = outcome.get_result()
    extra = getattr(report, 'extra', [])

    if report.when == 'call' or report.when == "setup":
        xfail = hasattr(report, 'wasxfail')
        if (report.skipped and xfail) or (report.failed and not xfail):
            file_name = report.nodeid.replace("::", "_") + ".png"
            # 从测试用例实例中获取driver
            driver = None
            if hasattr(item, 'instance'):
                driver = getattr(item.instance, 'driver', None)
            # 仅当driver存在时才执行截图
            if driver:
                _capture_screenshot(driver, file_name)
                html = '<div><img src="%s" alt="screenshot" style="width:304px;height:228px;" ' \
                       'onclick="window.open(this.src)" align="right"/></div>' % file_name
                extra.append(pytest_html.extras.html(html))
        report.extra = extra


def _capture_screenshot(driver, name):
    driver.get_screenshot_as_file(name)

方案2：修复全局变量逻辑（兼容原有写法） #

如果坚持使用全局driver，需增加空值判断，并在setup fixture中处理异常场景：

1. 修改setup fixture，确保无论初始化是否成功都能安全销毁driver：

@pytest.fixture(scope="class", autouse=True)
def setup(request):
    global driver
    driver = None
    service_obj = Service("/Users/ibrahim/SeleniumProjects/BrowserDrivers/chromedriver")
    browser_name = request.config.getoption("browser_name")

    try:
        if browser_name == "chrome":
            driver = webdriver.Chrome(service=service_obj)
        elif browser_name == "safari":
            driver = webdriver.Safari()
        elif browser_name == "firefox":
            driver = webdriver.Firefox()
        
        if driver:
            driver.get("https://rahulshettyacademy.com/angularpractice/")
            driver.implicitly_wait(5)
            driver.maximize_window()
            request.cls.driver = driver
        yield 
    finally:
        # 仅当driver存在时执行关闭操作
        if driver:
            driver.close()

2. 修改截图函数，增加空值判断：

def _capture_screenshot(name):
    global driver
    if driver is not None:
        driver.get_screenshot_as_file(name)

内容的提问来源于stack exchange，提问作者djoker