Selenium 与 Python：陈旧的元素引用异常

Question

从工作测试驱动开发与Python，和迁移后立即运行功能测试的时候我目前遇到“StaleElementReferenceException”。这是错误的全文：

ERROR: test_start_and_retrieve_list (__main__.NewVisitorTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "functional_tests.py", line 53, in test_start_and_retrieve_list
    rows = table.find_elements_by_tag_name('tr')
  File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/remote/webelement.py", line 237, in find_elements_by_tag_name
    return self.find_elements(by=By.TAG_NAME, value=name)
  File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/remote/webelement.py", line 527, in find_elements
    {"using": by, "value": value})['value']
  File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/remote/webelement.py", line 493, in _execute
    return self._parent.execute(command, params)
  File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/remote/webdriver.py", line 256, in execute
    self.error_handler.check_response(response)
  File "/usr/local/lib/python3.5/dist-packages/selenium/webdriver/remote/errorhandler.py", line 194, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.StaleElementReferenceException: Message: The element reference of <table id="id_list_table"> stale: either the element is no longer attached to the DOM or the page has been refreshed


----------------------------------------------------------------------
Ran 1 test in 8.735s

FAILED (errors=1)

这是测试：

from selenium import webdriver
from selenium.webdriver.common.keys import Keys
import unittest

class NewVisitorTest(unittest.TestCase): 

    def setUp(self):
        self.browser = webdriver.Firefox()
        self.browser.implicitly_wait(3)

    def tearDown(self):
        self.browser.close()

    def check_for_row(self, row_text):
        table = self.browser.find_element_by_id('id_list_table')
        rows = table.find_elements_by_tag_name('tr')
        self.assertIn(row_text, [row.text for row in rows])

    def test_start_and_retrieve_list(self):    
        self.browser.get('http://localhost:8000')

        self.assertIn('To-Do', self.browser.title)
        header_text = self.browser.find_element_by_tag_name('h1').text
        self.assertIn('To-Do', header_text)

        inputbox = self.browser.find_element_by_id('id_new_item')
        self.assertEqual(
            inputbox.get_attribute('placeholder'),
            'Enter a to-do item'
        )

        inputbox.send_keys('Buy peacock feathers')

        inputbox.send_keys(Keys.ENTER)
        self.check_for_row('1: Buy peacock feathers')

        inputbox = self.browser.find_element_by_id('id_new_item')
        inputbox.send_keys('Use peacock feathers to make a fly')
        inputbox.send_keys(Keys.ENTER)

        table = self.browser.find_element_by_id('id_list_table')
        rows = table.find_elements_by_tag_name('tr')
        self.check_for_row('1: Buy peacock feathers')
        self.check_for_row('2: Use peacock feathers to make a fly')

        self.fail('Finish the test!')

if __name__ == '__main__':
    unittest.main(warnings='ignore')

如何配置测试以防止这种情况发生？Selenium 自己的页面说当页面刷新时会出现这个问题，但这是应用程序逻辑的必要部分，因为它是迄今为止配置的。

Answer 1

我已经使用硒有一段时间了，所以我理解陈旧元素异常的挣扎。虽然并不完美，但 selenium 提供了一系列“等待”命令来允许网站加载完成。不幸的是，它并不完美，因为每次运行加载可能需要不同的时间，但这些是 selenium 提供的工具。