使用Python学习selenium测试工具-4：查找元素

web通常包含了Hyper Text Markup Language (HTML)、Cascading Style Sheets (CSS)和JavaScript。本节主要内容如下：

• 了解更多Selenium webDriver查找元素的知识

• 使用各种浏览器提供的开发工具找到和定位元素

• 多种发现元素的方法：ID、Name、类属性值、XPath、CSS选择器

• Selenium webDriver中的各种find_element_by方法。

一般的浏览器都有查看源码的功能 。

使用开发工具发现定位器

Firefox的插件Firebug是个好帮手，可以F12或者右键点击元素选择“Inspect Element with Firebug”打开。Firefox的搜素框还可以对XPath或CSS进行查找。

Chrome中可以F12或者右键点击元素选择“Inspect Element”的方式查看代码。查找功能也和Firefox类似。Internet Explorer也有类似功能，不再赘述。

元素查找

find_element_by*系列方法在找到元素的时候返回WebElement实例，否则产生NoSuchElementException异常。另外find_elements_by*系列方法可以一次返回多个元素。

driver.find_element_by_css_selector(‘#search’)

Method	Description	Argument	Example
find_element_by_id(id)	This method finds an element by the ID attribute value	id: The ID of the element to be found	driver.find_element_by_id(‘search’)
find_element_by_name(name)	This method finds an element by the name attribute value	name: The name of the element to be found	driver.find_element_by_name(‘q’)
find_element_by_class_name(name)	This method finds an element by the class attribute value	name: The class name of the element to be found	driver.find_element_by_class_name(‘input-text’)
find_element_by_tag_name(name)	This method finds an element by its tag name	name: The tag name of the element to be found	driver.find_element_by_tag_name(‘input’)
find_element_by_xpath(xpath)	This method finds an element using XPath	xpath: The xpath of the element to be found	driver.find_element_by_xpath(‘form[0]/div[0]/input[0]’)
find_element_by_css_selector(css_selector)	This method finds an element by the CSS selector	css_selector: The CSS selector of the element to be found
find_element_by_link_text(link_text)	This method finds an element by the link text	link_text: The text of the element to be found	driver.find_element_by_link_text(‘Log In’)
find_element_by_partial_link_text(link_text)	This method finds an element by a partial match of its link text	link_text: The text to match part of the text of the element	driver.find_element_by_partial_link_text(‘Log’)

通过id、name、类属性是最建议，也是最快速的查找方法，尤其是id和name。其次使用tag和链接文本，万不得已才使用xpath和css。

XPath即为XML路径语言（XML Path Language），它是一种用来确定XML文档中某部分位置的语言。参考：XPath维基百科介绍 以及w3schools的Xpath介绍，zvon的XPath 1.0介绍。参考书籍：Selenium Testing Tools        Cookbook。注意XPath的速度会比CSS还慢，不过支持向前向后定义和相对路径。

层叠样式表（英语：Cascading Style Sheets，简写CSS），又称串样式列表、层次结构式样式表文件，一种用来为结构化文档（如HTML文档或XML应用）添加样式（字体、间距和颜色等）的计算机语言。参考CSS维基百科介绍，w3schools之CSS介绍 和

实例

import unittest
from selenium import webdriver

class HomePageTest(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        # create a new Firefox session
        cls.driver = webdriver.Firefox()
        cls.driver.implicitly_wait(30)
        cls.driver.maximize_window()

        # navigate to the application home page
        cls.driver.get('http://demo-store.seleniumacademy.com/')

    def test_search_text_field_max_length(self):
        # get the search textbox
        search_field = self.driver.find_element_by_id('search')

        # check maxlength attribute is set to 128
        self.assertEqual('128', search_field.get_attribute('maxlength'))

    def test_search_button_enabled(self):
        # get Search button
        search_button = self.driver.find_element_by_class_name('button')

        # check Search button is enabled
        self.assertTrue(search_button.is_enabled())

    def test_my_account_link_is_displayed(self):
        # get the Account link
        account_link = self.driver.find_element_by_link_text('ACCOUNT')

        # check My Account link is displayed/visible in the Home page footer
        self.assertTrue(account_link.is_displayed())

    def test_account_links(self):
        # get the all the links with Account text in it
        account_links = self.driver.\
            find_elements_by_partial_link_text('ACCOUNT')

        # check Account and My Account link is displayed/visible in the Home page footer
        self.assertTrue(len(account_links), 2)

    def test_count_of_promo_banners_images(self):
        # get promo banner list
        banner_list = self.driver.find_element_by_class_name('promos')

        # get images from the banner_list
        banners = banner_list.find_elements_by_tag_name('img')

        # check there are 3 banners displayed on the page
        self.assertEqual(3, len(banners))

    def test_vip_promo(self):
        # get vip promo image
        vip_promo = self.driver.\
            find_element_by_xpath("//img[@alt='Shop Private Sales - Members Only']")

        # check vip promo logo is displayed on home page
        self.assertTrue(vip_promo.is_displayed())
        # click on vip promo images to open the page
        vip_promo.click()
        # check page title
        self.assertEqual("VIP", self.driver.title)

    def test_shopping_cart_status(self):
        # check content of My Shopping Cart block on Home page
        # get the Shopping cart icon and click to open the Shopping Cart section
        shopping_cart_icon = self.driver.\
            find_element_by_css_selector('div.header-minicart span.icon')
        shopping_cart_icon.click()

        # get the shopping cart status
        shopping_cart_status = self.driver.\
            find_element_by_css_selector('p.empty').text
        self.assertEqual('You have no items in your shopping cart.',
                          shopping_cart_status)
        # close the shopping cart section
        close_button = self.driver.\
            find_element_by_css_selector('div.minicart-wrapper a.close')
        close_button.click()

    @classmethod
    def tearDownClass(cls):
        # close the browser window
        cls.driver.quit()

if __name__ == '__main__':
    unittest.main(verbosity=2)

执行结果：

# python        homepagetest.py
test_account_links (__main__.HomePageTest) ... ok
test_count_of_promo_banners_images (__main__.HomePageTest) ... ok
test_my_account_link_is_displayed (__main__.HomePageTest) ... ok
test_search_button_enabled (__main__.HomePageTest) ... ok
test_search_text_field_max_length (__main__.HomePageTest) ... ok
test_shopping_cart_status (__main__.HomePageTest) ... ok
test_vip_promo (__main__.HomePageTest) ... ok
----------------------------------------------------------------------
Ran 7 tests in 77.086s

OK