Useful tools for writing Selenium tests
I've been writing a lot of Selenium tests lately and I've been using some tools that I find extremely useful for composing table-style tests. Let me start by saying that writing GUI-based tests for Web apps is no fun, no matter what your testing tool is. You need to navigate through pages, fill and submit forms, and verify that certain elements are present on the pages. Doing all this manually can quickly become tedious and kill whatever joy you may find in testing.
If you're writing Selenium tests, these activities are, if not fun, at least tolerable due to the existence of the Selenium Recorder ("the Selenium Recorder -- can't imagine life as a Web app tester without it" seems like a good line for a commercial :-)
The Selenium Recorder (which I'll refer to as SelRec from now on) is a Firefox extension that you launch via the Tools menu. It intercepts Web browsing actions such as opening a URL, clicking on a link, entering text in a field form, selecting a drop-down menu item, submitting a form, etc., and it records them in HTML format, ready to be copied and pasted into your Selenium test files. What I find most remarkable about this is that I don't need to worry about identifying HTML elements in order to find a suitable Selenium locator such as an XPath expression, or a DOM expression. For example, SelRec is smart enough to identify links using the simplest locator expression that uniquely identifies a link. If the name of the link is unique, SelRec will use it. If several links have the same name, SelRec will automatically use an XPath expression that uniquely identifies each link.
SelRec can also help with certain Selenium assertion commands. For example, if you highlight the text on a Web page and right-click, you'll see a menu item called "Append Selenium command" which allows you to add one of the following 2 commands to your test table:
- verifyTextPresent|highlighted text|
- verifyTitle|title of the current Web page|
I would guess that most of the testing you're doing with Selenium consists in opening URLs, clicking on various page elements, submitting forms and asserting that some text is present on a Web page or that a Web page has a certain title. Since all these actions and verifications are supported by SelRec out of the box, your life as a tester suddenly becomes a bit easier.
One problem with the "verifyTextPresent" command is that it doesn't support regular expressions. Many times you do need to verify that a specific chunk of text on your page conforms to a regular expression. For this, you need the "verifyText" command, which takes as its first argument the locator of the HTML element whose text you need to verify. This is when things become a bit hairy: you somehow need to identify that element. You can always try to do it in your head by eye-balling the HTML source of the page and trying to come up with the right XPath expression. But fortunately there's an easier way.
At this point, I'm glad to be able to point you to another sanity-saving tool: XPath Checker, which is also a Firefox extension. After installing it, you highlight any text on a Web page, right-click and choose "View XPath". A Firefox window will pop up with an entry field containing an XPath expression, as identified by the tool, and with the text matching that expression. This window allows you to interactively change the XPath expression and see the text that it matches. It's great for playing with and learning XPath (BTW, here is a great XPath tutorial).
Together, the Selenium Recorder and the XPath Checker tools will allow you to easily write the vast majority of your Selenium tests. For more advanced functionality, I refer you to the many Selenium user extensions contributed by people active in the Selenium community. For some nifty Ajax testing (if I may say so myself), see also this blog post of mine.
Note that XPath expressions don't work that well in Internet Explorer. If browser compatibility is high on your list, then you probably need to identify HTML elements via their DOM locations. For that, you can use the DOM Locator extension which ships with Firefox, but you can also peek at the XPath expression generated by the XPath Checker and try to come up with the equivalent DOM expression. Camino, a Mac-specific browser, doesn't seem to have this problem, so you can very easily write your Selenium tests using Firefox with its extensions, then run them in Camino (Titus and I did just that when testing our PyCon tutorial app).
To wrap this thing up, here's an example of using the SelRec and the XPath Checker. Let's assume you want to test some of the search functionality of amazon.com. Note that you can't do this with table-mode Selenium unless you work for amazon.com, because you need to deploy your tests on the amazon.com Web app servers. But for the sake of this example, I just want to illustrate how to use the tools when testing a complex Web site.
Here's a test table that was generated with the Selenium Recorder and that I edited with Mozilla Composer in order to add my own verifyText commands, for which I used XPath expressions that were generated with the XPath Checker:
|verifyTitle||Amazon.com: Online Shopping for Electronics, Apparel, Computers, Books, DVDs & more|
|clickAndWait||//input[@type='image' and @alt='Go']|
|verifyTitle||Amazon.com: All Products Search Results: python|
|verifyText||//*[@id='Td:0']/table/tbody/tr/td/table/tbody/tr/td/table/tbody/tr||Learning Python, Second Edition by Mark Lutz and David Ascher (Paperback - Dec 2003)|
|click||link=Learning Python, Second Edition|
|verifyTitle||Amazon.com: Learning Python, Second Edition: Books: Mark Lutz,David Ascher|
|verifyText||/html/body/table/tbody/tr/td/div||regexp:Buy this book with .* by Alex Martelli today!|
The Selenium Recorder can help even when adding your own verifyText commands. Here's how I did it:
- I highlighted the text I wanted to verify on the Web page under test, then I right-clicked and I chose "Append Selenium command" -> verifyTextPresent "highlighted text"
- I saved the file generated by SelRec, then I opened it in Mozilla Composer
- The last row in the file was something like |verifyTextPresent|some text||
- I edited the row and I replaced "verifyTextPresent" with "verifyText", then I did a cut and paste of "some text" from the second to the third cell
- I highlighted again the text on the Web page under test, I right-clicked and I chose "View XPath", then I copied the XPath expression generated by the XPath Checker in the second cell of the table row
- The row now looks something like |verifyText|//some/xpath/expression|some text|
- At this point, if you need to make sure that "some text" matches a regular expression, you can start the third cell with "regexp:" followed by the regular expression (for example, in the table above, I used the somewhat-contrived "regexp:Buy this book with .* by Alex Martelli today!")
- Patrick Lightbody, the maintainer of openqa.org, where Selenium is hosted, reminded me that the Selenium Recorder project is now called the Selenium IDE and is hosted at OpenQA. There is no release of the Selenium IDE yet, but you'll find out when it will be available, I promise :-)
- Speaking of the upcoming release for the Selenium Recorder/IDE, one feature I'd like to see added is the capability of adding verifyText commands, with the XPath expression corresponding to the highlighted text -- an unification of the XPath Checker functionality with the current verifyText functionality in SelRec
- Luke Closs points out that he wrote a tool that allows him to write Selenium tests in simple wiki-like tables, then it will convert them into HTML and auto-create a TestSuite.html for him; you can find more info about Luke's Perl-based tool at awesnob.com/selutils.
- An anonymous commenter points out XPather as another Firefox extension that's superior in his/her opinion to the XPath Checker extension