Functional Testing with Selenium WebDriver and Selector in Python

In this post, we shall be exploring functional/integration/system testing via selenium in Python. The post assumes, that you have a basic understanding of the terminologies of test driven development, you know basic python. The post does not assume any basic knowledge of selenium and is aimed to get you started with selenium with python. A brief overview followed by a simple demo.

To install selenium all you need to do is pip install selenium

To carry out functional testing, we need three things:

  1. Browser

  2. Automated Custom Key Actions

  3. Use 1,2 to assert some predefined behavior

1. Getting hold of a browser

from selenium import webdriver provides us a WebDriver implementation, currently supported ones are Firefox and Chrome and from selenium.webdriver.common.keys import Keys provides with common keys. (On mac brew install chromedriver fixes the Chrome driver issue)

We want a driver instance and we get it via driver = webdriver.Firefox().

2. Simulating KeyPress

To simulate a key press at a location we need to do 2 things:

2.1 get the element

Element can be a form field where one would want to type some text, or probably a submit button. There are various methods:

find_element_by_id find_element_by_xpath find_element_by_link_text find_element_by_name find_element_by_tag_name find_element_by_css_selector

Given an html structure as <input type="text" name="get_text" id="text-id"> To get the above form element all we would want to do is elem = driver.find_element_by_name("get_text") elem = driver.find_element_by_id("text-id") elem = driver.find_element_by_xpath("//input[@id='text-id']") ..... There are no hard and fast rules as to which kind of selector you want to choose. However the following table simplifies locating html elements.
Method Usecase Returns
locating by Id when id attribute of element is known returns the first element with id attribute matching
locating by Name when name attribute of element is known returns the first element with name attribute matching
locating by hyperlink text when link text used within an anchor tag is known returns the first element with the link text value matching the location is returned
locating by XPath when there is confusion in chosing name/id returns the absolute element

Few things to keep in mind for using XPaths is that, they should be used when the name or id for an element is not available. XPaths should be relative rather than absolute, this helps making the test more robust, sice a minor change before the element in the DOM structure, might cause the XPath selector to fail. The recommended method is to find the id/name of the nearest element and then calculate the relative XPath from the id.

2.2 trigger the key press

To enter a value in the input form now, that we already have the element, we use elem.send_keys("Some random text inside the form field")

When everything is done we can quit the browser by driver.close

3. Asserting some values

Having performed the above steps, we would want to test features. Probably clicking a button and verifying some data on the new page, or some ajax response. The basic lies in asserting, eg. assert "Page Title". Functional testing revolves all around the above three steps. Now that we have basics in place in the second part of the post, we will play around with a simple app and write functional tests.

Simple Demo

If you move over to we have a simple form, lets move over to it, and automate the form submission using selenium. The basic steps would be:

  1. Basic Imports in place
  2. Open the url, in a web driver
  3. Fetch the form elements and trigger key press
  4. Press the submit button
  5. Assert the changes in the dom.

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

#initializing driver, and opening the webpage driver = webdriver.Firefox() url = "" driver.get(url)

# defining selectors name_element = driver.find_element_by_name("name") email_element = driver.find_element_by_name("email") subject_element = driver.find_element_by_name("subject") message_element = driver.find_element_by_name("message") send_btn_element = driver.find_element_by_id("submit")

# triggering key press name_element.send_keys("John Doe") email_element.send_keys("[email protected]") subject_element.send_keys("Went through Selenium Article") message_element.send_keys("Nice tut bro!") submit_success_text_elem = driver.find_element_by_tag_name('h4') success_msg = "Thank you, your message has been sent." assert submit_success_text_elem.text == success_msg

Bingo, you have done some good stuff!


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