Posts Tagged ‘css’

Why CSS Locators are the way to go vs XPath

May 17th, 2011 by Ashley Wilson

Last week, our own Santiago Suarez Ordoñez gave a presentation to the San Francisco Selenium Meetup group that convinced us all to say no (for the most part) to XPath and yes to CSS Locators in our Selenium tests.

In his role as official Sauce Ninja and as a prolific poster in the Selenium forums, Santi has helped more users solve locator issues than possibly anyone else in the world. He’s previously written a number of blog posts on ways to improve locator performance. As Sauce CEO John Dunham puts it, “If there was a foursquare mayorship for locators, Santi would have it for a lifetime.”

Drawing from this experience, he gave us these four reasons for using CSS Locators:

1. They’re faster
2. They’re more readable
3. CSS is jQuery’s locating strategy
4. No one else uses XPATH anyways!

I can’t speak for everyone, but Santi sure sold me on point number one when he showed off the performance metric script he wrote a script that tested the speed of XPath vs the speed of CSS Locators. There wasn’t much of a difference in Firefox, Safari, or Chrome, but with IE, the results were undeniable. Take a look:

To underscore this even further, he also recorded a video in Sauce OnDemand that uses one heck of a cute kitten to illustrate just how slow XPath can be. The cat’s paw movements represent the test clicking through the different locators. The first batch of clicks uses CSS Locators and completes in under 30 seconds. The second batch, the XPath one, continues on for another eight minutes. Eight minutes!

During the rest of the presentation, Santi dives into writing both basic and more advanced CSS Locators. He also spends some time talking about when you shouldn’t use CSS Locators (yes, there are a few cases where it is not the right tool for the job). To see the talk in its entirety, check out the recording below. And if you’re thinking of switching over from XPath, but unsure of how to go about it, check out the nifty tool Santi wrote called cssify. It does the handy work of translating your XPaths to CSS automatically.

Helpful links
View Santi’s Presentation Slides
Follow him on Twitter
Follow Sauce on Twitter
Join the San Francisco Selenium Meetup group!

Enjoy!

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Selenium Tips: CSS Selectors in Selenium Demystified

January 29th, 2010 by Santiago Suarez Ordoñez

Following my previous TOTW about improving your locators, this blog post will show you some advanced CSS rules and pseudo-classes that will help you move your XPATH locators to CSS, a native approach on all browsers.

Next sibling

Our first example is useful for navigating lists of elements, such as forms or ul items. The next sibling will tell selenium to find the next adjacent element on the page that’s inside the same parent. Let’s show an example using a form to select the field after username.


</input>
</input>

Let’s write a css selector that will choose the input field after “username”. This will select the “alias” input, or will select a different element if the form is reordered.

css=form input.username + input

Attribute values

If you don’t care about the ordering of child elements, you can use an attribute selector in selenium to choose elements based on any attribute value. A good example would be choosing the ‘username’ element of the form without adding a class.


</input>
</input>
</input>
</input>

We can easily select the username element without adding a class or an id to the element.

css=form input[name='username']

We can even chain filters to be more specific with our selections.

css=input[name='continue'][type='button']

Here Selenium will act on the input field with name=”continue” and type=”button”

Choosing a specific match

CSS selectors in Selenium allow us to navigate lists with more finess that the above methods. If we have a ul and we want to select its fourth li element without regard to any other elements, we should use nth-child or nth-of-type.

    
<p>Heading</p>

  • Cat
    • 

  • Dog
    • 

  • Car
    • 

  • Goat
    •

If we want to select the fourth li element (Goat) in this list, we can use the nth-of-type, which will find the fourth li in the list.

css=ul#recordlist li:nth-of-type(4)

On the other hand, if we want to get the fourth element only if it is a li element, we can use a filtered nth-child which will select (Car) in this case.

css=ul#recordlist li:nth-child(4)

Note, if you don’t specify a child type for nth-child it will allow you to select the fourth child without regard to type. This may be useful in testing css layout in selenium.

css=ul#recordlist *:nth-child(4)

Sub-string matches

CSS in Selenium has an interesting feature of allowing partial string matches using ^=, $=, or *=. I’ll define them, then show an example of each:

^= Match a prefix
$= Match a suffix
*= Match a substring 
css=a[id^='id_prefix_']

A link with an “id” that starts with the text “id_prefix_”

css=a[id$='_id_sufix']

A link with an “id” that ends with the text “_id_sufix”

css=a[id*='id_pattern']

A link with an “id” that contains the text “id_pattern”

Matching by inner text

And last, one of the more useful pseudo-classes, :contains() will match elements with the desired text block:

css=a:contains('Log Out')

This will find the log out button on your page no matter where it’s located. This is by far my favorite CSS selector and I find it greatly simplifies a lot of my test code.

Tune in next week for more Selenium Tips from Sauce Labs.

Sauce Labs created Sauce OnDemand, a Selenium-based testing service that allows you to test across multiple browsers in the cloud. With Selenium IDE and Selenium RC compatibilities, you can get complete cross-platform browser testing today.

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