Selenium is an application that automates web browsers, helping you test your web application from a user perspective, in an automated manner. These properties make Selenium tests a perfect fit for validating your js-level functionality and implementing acceptance tests.
Of course, it has some drawbacks: you need to run your application from another process, which gives you some pain with checking the backend state of things. The tests might be quite slow, and - if you don't write them well - extremely fragile.
However, starting with basic Selenium tests is very simple, which I'm going to prove below. We will create a trivial website, with a single element only: a link to Google. Next, we will implement a Selenium test that makes sure this indeed happens.
Prepare the environment
We will work in a virtualenv called "seltest". If you don't know what virtualenv is, you likely want to read this first. Enter the directory of your choice and run the following commands:
virtualenv --no-site-packages .
We will work from within the seltest directory, so that we don't need to activate the virtualenv, and instead call our binaries by "bin/python" or "bin/pip".
Let's download the Selenium executable and its python bindings:
bin/pip install selenium
You can already play with Selenium. First, start another terminal window and run:
java -jar selenium-server-standalone-2.0a4.jar
Then from our main terminal:
>>> from selenium.remote import connect
>>> from selenium import FIREFOX
>>> browser = connect(FIREFOX) # this will run the browser
>>> browser.get("http://www.yahoo.com") # you should see the browser navigating to yahoo
>>> browser.close() # this will close the session
Prepare and run the website
The website will consist of a single link, we can skip all the obligatory html boilerplate at this stage. Save the text
<a href="http://google.com">Go to Google</a>
into a file index.html, and from another terminal (yes, you will need three terminal windows) run:
Python -m SimpleHTTPServer
This will start serving your page on the port 8000, you can visit the page from your web browser on http://localhost:8000/
Implement the test
Open the file selenium_test.py in your editor of choice and dump the following
from selenium.remote import connect
from selenium import FIREFOX
self.browser = connect(FIREFOX)
link = self.browser.find_element_by_partial_link_text("Google")
if __name__ == "__main__":
The setUp and tearDown methods manage the browser session, and the actual test lives in the test_simple method. We are using four methods from the browser object: get, find_element_by_partial_link_text, click and get_title. In case you wonder where these come from, look for the WebDriver class definition. You can find it in lib/python2.6/site-packages/selenium/remote/webdriver.py in your environment.
Run the test
Now, you are ready to run your test.
You should see something along the lines of:
$ bin/python selenium_test.py
Ran 1 test in 5.521s
Which indicates, that all your tests passed correctly.