Redux Note: I originally wrote a similar article to this before going on parental leave about six weeks ago. Whilst I didn’t intend to offend, it seemed that a few people took my article the wrong way. I understand that a lot of effort goes into creating a web testing API, but that doesn’t mean that everyone will agree with what you’ve made.
Sadly, an anonymous coward attacked myself and the company who I work (even though I don’t mention that company on this blog), so for the first time in this blog’s history, I have had to turn comment moderation on. I am sorry to the other genuine commenters whose comments have been lost in transition, and now have to wait for their new comments to be approved.
Since then I have received numerous emails asking where my article went, and commenting that people found it interesting and worthwhile. So I have decided to repost this article, hopefully with a little less contention this time around, making it clear, this is my opinion and experience: YMMV.
As a consultant I get to see and work on a lot of automated testing solutions using different automated web testing APIs. Lately I’ve been thinking about how these APIs are different and what makes them so.
My main interest is in ruby, and fortunately ruby has three solid examples of three different kinds of web testing APIs, two of which extend the lowest level API: selenium-webdriver.
I’ll (try to) explain here what I consider to be three kinds of automated web testing APIs and where I consider the sweet spot to be and and why.
A meaty example
As a carnivore, I thought I would explain my concept in terms I can relate to. If you’re a beef eater, there are many different kinds of beef that you can use to make some tasty food to eat. I’ll use three different kinds of beef for my example. The first (rawest) kind would involve getting a beef carcass and filleting it yourself to eventually make some edible food. The second kind of beef you could use is beef that is already in a slightly usable form, but you can then use yourself to make some edible food. For example, you can buy minced beef at a butcher, and then make your own hamburger patties, taco fillings etc from it. The final type of beef you could use is beef that has already been prepared so you can directly consume it, for example, sausages which can be cooked and consumed as is.
I consider these three examples of different kinds of beef to roughly correlate to automated web testing APIs, of which I also consider to be three kinds of.
The first is a Web Driver API, which is the rawest form of an API, its job is to drive a browser by issuing it commands. It provides a high level of user control, but like filleting a beef carcass it’s more ‘work’. An example in ruby of this API is the selenium-webdriver API, which controls the browser using the webdriver drivers.
The second kind of automated web testing API is the Browser API, which is a higher level API but still provides user control. This is the minced beef of APIs, as whilst it’s in a more usable form than a carcass, you still have a lot of control (and potential to what you can do with it). An example in ruby of this API is the watir-webdriver API, which uses the underlying selenium-webdriver carcass to control the browser.
The final kind of automated web testing API is the Web Form DSL (Domain Specific Language) which is a very high level API that provides users with specific methods to automate web forms and their elements. This is the beef sausages of APIs as sometimes you feel like eating something else besides sausages, but it’s difficult to make anything else edible but sausages from sausages. An example in ruby of this Web Form DSL is the Capybara DSL.
Visually, this looks something like this:
Show me the code™
So exactly what do these APIs look like?
I knew you’d ask, that’s why I came prepared.
Say I want to accomplish a fairly basic scenario on my example Google Doc form:
- Start a browser
- Navigate to the watir-webdriver-demo form
- Check whether text field with id ‘entry_0’ exists (this should exist)
- Check whether text field with id ‘entry_99’ exists (this shouldn’t exist)
- Set a text field with id ‘entry_0’ to ‘1’
- Set a text field with id ‘entry_0’ to ‘2’
- Select ‘Ruby’ from select list with id ‘entry_1’
- Click the Submit button
This is how I would do it in the three different APIs:
# * Start browser
# * Navigate to watir-webdriver-demo form
# * Check whether text field with id 'entry_0' exists
# * Check whether text field with id 'entry_99' exists
# * Set text field with id 'entry_0' to '1'
# * Set text field with id 'entry_0' to '2'
# * Select 'Ruby' from select list with id 'entry_1'
# * Click the Submit button
benchmark 'selenium-webdriver' do
driver = Selenium::WebDriver.for :firefox
# doesn't exist
# doesn't exist
driver.find_element(:id, 'entry_0').send_keys '1'
driver.find_element(:id, 'entry_0').send_keys '2'
driver.find_element(:id, 'entry_1').find_element(:tag_name => 'option', :value => 'Ruby').click
benchmark 'watir-webdriver' do
b = Watir::Browser.start 'bit.ly/watir-webdriver-demo', :firefox
b.text_field(:id => 'entry_0').exists?
b.text_field(:id => 'entry_99').exists?
b.text_field(:id => 'entry_0').set '1'
b.text_field(:id => 'entry_0').set '2'
b.select_list(:id => 'entry_1').select 'Ruby'
b.button(:name => 'submit').click
benchmark 'capybara' do
session = Capybara::Session.new(:selenium)
session.has_field?('entry_0') # => true
session.has_no_field?('entry_99') # => true
session.fill_in('entry_0', :with => '1')
session.fill_in('entry_0', :with => '2')
session.select('Ruby', :from => 'entry_1')
This is how long they took for me to run:
user system total real
selenium-webdriver 1.810000 0.840000 22.130000 ( 73.123340)
watir-webdriver 1.940000 0.870000 24.380000 ( 79.388494)
capybara 1.950000 0.890000 24.080000 ( 79.920051)
Note: Capybara doesn’t always require a ‘session’, it’s only for non ruby rack applications, but since my example (Google) is not a rack application, as are most of the applications I test, my example must use the session.
When using ruby, why Watir-WebDriver is my sweet spot
I personally find Watir-WebDriver to be the most elegant solution, as the API is high enough for me to be highly readable/usable, but low enough to be powerful and for me to feel like I’m in control.
For example, being able to select an element by a explicit identifier (name, class name, id, anything) is a huge deal to me. I personally don’t like relying on the API to determine which selector to use: for example Capybara only supports name, id and label, but you can’t tell fill_in which specific one to choose: it appears to try each selector one by one until it finds it.
I have found that Watir-WebDriver also also provides lots of flexibility/neatness. For example: it’s the only API shown here that allows URLs to not have a ‘http://’ prefix (how many people do you know who type in http:// into a browser?).
In my opinion, the high level APIs like Capybara don’t provide enough control (for example – being able to specify the explicit selector), but the low level APIs like webdriver don’t provide enough functionality. This is evident when I am using a language other than ruby (like C#) when I find myself writing a large number of web element extension methods because webdriver doesn’t provide any of them. A .set method is a classic example, even Simon Stewart writes a clearAndType method in his examples even though he wrote webdriver which sadly misses it (you must call .clear, and .send_keys).
My biggest concern about high level field APIs
But my biggest issue with the high level APIs is that I’ve frequently seen them used to write test scripts that are step by step interactions with a web form. Instead of thinking of a business application as that, people see it as a series of forms that you ‘fill in’. This means people create scenarios like Aslak Hellesøy included in his recent post about cucumber web steps (which uses Capybara) and the problems it has created.
Scenario: Successful login
Given a user "Aslak" with password "xyz"
And I am on the login page
And I fill in "User name" with "Aslak"
And I fill in "Password" with "xyz"
When I press "Log in"
Then I should see "Welcome, Aslak"
I’m not saying it’s not possible to end up with something as ugly as above using other APIs, but I am saying the web form DSL style naturally relates to this: as the APIs look so similar to this style because that’s what the DSL was designed for: filling in forms. I’ve seen people frequently write generic, reusable cucumber steps to match the web form DSL like:
When /^I fill in "(.+)" with "(.+)"$/ do |value, field|
fill_in field, :with => value
But this means you end up with less readable, less maintainable test scripts rather than business readable executable specifications.
Ultimately what I am looking for in an automated web testing API is simplicity and full control. I personally find browser APIs like Watir-WebDriver and Watir give me this, and this is why I love them so. Your mileage may vary, you may like different styles of APIs better, but I’ve seen other APIs so badly abused by people not even thinking about it, so it makes sense to think about what you’re trying to achieve and whether what you’re doing is the right way.