为什么 splinter is_text_present() 会导致 Firefox 的间歇性 StaleElement

Question

将我的测试环境升级到最新版本的Selenium，splinter和Firefox后，我的一个测试现在使用Firefox失败了大约80%，如下所示：

Traceback (most recent call last):
  File "/Users/rbednark/Dropbox/git/quizme_website/questions/tests.py", line 103, in test_login_fails_incorrect_username
    "Your username and password didn't match. Please try again."
  File "/Users/rbednark/.virtualenvs/quizme-django-1.6.5/lib/python2.7/site-packages/splinter/driver/webdriver/__init__.py", line 302, in is_text_present
    self.driver.find_element_by_tag_name('body').text.index(text)
  File "/Users/rbednark/.virtualenvs/quizme-django-1.6.5/lib/python2.7/site-packages/selenium/webdriver/remote/webelement.py", line 73, in text
    return self._execute(Command.GET_ELEMENT_TEXT)['value']
  File "/Users/rbednark/.virtualenvs/quizme-django-1.6.5/lib/python2.7/site-packages/selenium/webdriver/remote/webelement.py", line 494, in _execute
    return self._parent.execute(command, params)
  File "/Users/rbednark/.virtualenvs/quizme-django-1.6.5/lib/python2.7/site-packages/selenium/webdriver/remote/webdriver.py", line 236, in execute
    self.error_handler.check_response(response)
  File "/Users/rbednark/.virtualenvs/quizme-django-1.6.5/lib/python2.7/site-packages/selenium/webdriver/remote/errorhandler.py", line 192, in check_response
    raise exception_class(message, screen, stacktrace)
StaleElementReferenceException: Message: The element reference is stale. Either the element is no longer attached to the DOM or the page has been refreshed.

请注意，同样的测试在使用Chrome和phantomjs时100%通过。 测试：

self.browser.visit(self.live_server_url)
self.assertEquals(self.browser.title, 'Quiz Me!')
self.browser.find_by_id('id_username')[0].fill(user)
self.browser.find_by_id('id_password')[0].fill(password)
# note that the following click() causes a page load
self.browser.find_by_value('login').click()
self.assertTrue(
      self.browser.is_text_present(
          "Your username and password didn't match. "
          "Please try again."
  )
)

火狐从49.0.2升级到50.1.0
硒从2.46.0升级为3.0.2
分裂从0.6.0升级到0.7.5
壁虎司机0.13.0
（以上均为发布时的最新版本）

Answer 1

我通过实现这个包装器解决了我的问题，该包装器在捕获异常时重试：

from selenium.common.exceptions import StaleElementReferenceException
def _loop_is_text_present(text, max_attempts=3):
    attempt = 1
    while True:
        try:
            return self.browser.is_text_present(text)
        except StaleElementReferenceException:
            if attempt == max_attempts:
                raise
            attempt += 1

灵感来源：http://darrellgrainger.blogspot.com/2012/06/staleelementexception.html

描述 StaleElementReferenceException 的 Selenium 源代码。