我在unittest中使用页面对象模型。有一个功能“截图”，它传入1个测试用例但在另一个测试用例中失败。这真的很奇怪，因为它传递了1个测试用例，我确信拥有所有的依赖性。
任何帮助都将不胜感激。
代码：
import ...
class Abc(unittest.TestCase):
def setUp(self):
self.xvfb = Xvfb(width=1280, height=720)
self.xvfb.start()
self.driver = webdriver.Firefox()
self.driver.get(data.baseurl)
def test_001_login(self):
home_page = home.HomePage(self.driver)
home_page.login(data.username, data.password)
home_page.screenshot(self.id() + "_login_success")
def test_002_test_scenario(self):
home_page = home.HomePage(self.driver)
self.driver.get(data.baseurl)
home_page.screenshot(self.id() + "_home_page")
def tearDown(self):
self.driver.close()
self.xvfb.stop
if __name__ == "__main__":
unittest.main()
错误：
Traceback (most recent call last):
File "/opt/buildagent/work/a8b2d36194b9264b/webtest/functions/alerts/test_alerts.py", line 65, in test_002_scenario
home_page.screenshot(self.id() + "_home_page")
File "/opt/buildagent/work/a8b2d36194b9264b/webtest/functions/home/home.py", line 107, in screenshot
self.driver.save_screenshot(tmp)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 1031, in save_screenshot
return self.get_screenshot_as_file(filename)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 1008, in get_screenshot_as_file
png = self.get_screenshot_as_png()
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 1040, in get_screenshot_as_png
return base64.b64decode(self.get_screenshot_as_base64().encode('ascii'))
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 1050, in get_screenshot_as_base64
return self.execute(Command.SCREENSHOT)['value']
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/webdriver.py", line 312, in execute
self.error_handler.check_response(response)
File "/usr/local/lib/python2.7/dist-packages/selenium/webdriver/remote/errorhandler.py", line 242, in check_response
raise exception_class(message, screen, stacktrace)
WebDriverException: Message: Failed to decode response from marionette