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Speeding up multi-browser Selenium Testing using concurrency

I haven’t used Selenium for awhile, so I took some time to dig into the options to get some mainline tests running against Caliper in multiple browsers. I wanted to be able to test a variety of browsers against our staging server before pushing new releases. Eventually this could be integrated into Continuous Integration (CI) or Continuous Deployment (CD).

The state of Selenium testing for Rails is currently in flux:

So there are multiple gems / frameworks:

I decided to investigate several options to determine which is the best approach for our tests.

selenium-on-rails

I originally wrote a couple example tests using the selenium-on-rails plugin. This allows you to browse to your local development web server at ‘/selenium’ and run tests in the browser using the Selenium test runner. It is simple and the most basic Selenium mode, but it obviously has limitations. It wasn’t easy to run many different browsers using this plugin, or use with Selenium-RC, and the plugin was fairly dated. This lead me to try simplest next thing, selenium-client

open '/'
assert_title 'Hosted Ruby/Rails metrics - Caliper'
verify_text_present 'Recently Generated Metrics'

click_and_wait "css=#projects a:contains('Projects')"
verify_text_present 'Browse Projects'

click_and_wait "css=#add-project a:contains('Add Project')"
verify_text_present 'Add Project'

type 'repo','git://github.com/sinatra/sinatra.git'
click_and_wait "css=#submit-project"
verify_text_present 'sinatra/sinatra'
wait_for_element_present "css=#hotspots-summary"
verify_text_present 'View full Hot Spots report'

view this gist

selenium-client

I quickly converted my selenium-on-rails tests to selenium-client tests, with some small modifications. To run tests using selenium-client, you need to run a selenium-RC server. I setup Sauce RC on my machine and was ready to go. I configured the tests to run locally on a single browser (Firefox). Once that was working I wanted to run the same tests in multiple browsers. I found that it was easy to dynamically create a test for each browser type and run them using selenium-RC, but that it was increadly slow, since tests run one after another and not concurrently. Also, you need to install each browser (plus multiple versions) on your machine. This led me to use Sauce Labs’ OnDemand.

browser.open '/'
assert_equal 'Hosted Ruby/Rails metrics - Caliper', browser.title
assert browser.text?('Recently Generated Metrics')

browser.click "css=#projects a:contains('Projects')", :wait_for => :page
assert browser.text?('Browse Projects')

browser.click "css=#add-project a:contains('Add Project')", :wait_for => :page
assert browser.text?('Add Project')

browser.type 'repo','git://github.com/sinatra/sinatra.git'
browser.click "css=#submit-project", :wait_for => :page
assert browser.text?('sinatra/sinatra')
browser.wait_for_element "css=#hotspots-summary"
assert browser.text?('View full Hot Spots report')

view this gist

Using Selenium-RC and Sauce Labs Concurrently

Running on all the browsers Sauce Labs offers (12) took 910 seconds. Which is cool, but way too slow, and since I am just running the same tests over in different browsers, I decided that it should be done concurrently. If you are running your own Selenium-RC server this will slow down a lot as your machine has to start and run all of the various browsers, so this approach isn’t recommended on your own Selenium-RC setup, unless you configure Selenium-Grid. If you are using  Sauce Labs, the tests run concurrently with no slow down. After switching to concurrently running my Selenium tests, run time went down to 70 seconds.

My main goal was to make it easy to write pretty standard tests a single time, but be able to change the number of browsers I ran them on and the server I targeted. One approach that has been offered explains how to setup Cucumber to run Selenium tests against multiple browsers. This basically runs the rake task over and over for each browser environment.

Althought this works, I also wanted to run all my tests concurrently. One option would be to concurrently run all of the Rake tasks and join the results. Joining the results is difficult to do cleanly or you end up outputting the full rake test output once per browser (ugly when running 12 times). I took a slightly different approach which just wraps any Selenium-based test in a run_in_browsers block. Depending on the options set, the code can run a single browser against your locally hosted application, or many browsers against a staging or production server. Then simply create a separate Rake task for each of the configurations you expect to use (against local selenium-RC and Sauce Labs on demand).

I am pretty happy with the solution I have for now. It is simple and fast and gives another layer of assurances that Caliper is running as expected. Adding additional tests is simple, as is integrating the solution into our CI stack. There are likely many ways to solve the concurrent selenium testing problem, but I was able to go from no Selenium tests to a fast multi-browser solution in about a day, which works for me. There are downsides to the approach, the error output isn’t exactly the same when run concurrently, but it is pretty close.  As opposed to seeing multiple errors for each test, you get a single error per test which includes the details about what browsers the error occurred on.

In the future I would recommend closely watching Webrat and Capybara which I would likely use to drive the Selenium tests. I think the eventual merge will lead to the best solution in terms of flexibility. At the moment Capybara doesn’t support selenium-RC, and the tests I originally wrote didn’t convert to the Webrat API as easily as directly to selenium-client (although setting up Webrat to use Selenium looks pretty simple). The example code given could likely be adapted easily to work with existing Webrat tests.

namespace :test do
  namespace :selenium do

    desc "selenium against staging server"
    task :staging do
      exec "bash -c 'SELENIUM_BROWSERS=all SELENIUM_RC_URL=saucelabs.com SELENIUM_URL=http://caliper-staging.heroku.com/  ruby test/acceptance/walkthrough.rb'"
    end

    desc "selenium against local server"
    task :local do
      exec "bash -c 'SELENIUM_BROWSERS=one SELENIUM_RC_URL=localhost SELENIUM_URL=http://localhost:3000/ ruby test/acceptance/walkthrough.rb'"
    end
  end
end

view this gist

require "rubygems"
require "test/unit"
gem "selenium-client", ">=1.2.16"
require "selenium/client"
require 'threadify'

class ExampleTest  1
      errors = []
      browsers.threadify(browsers.length) do |browser_spec|
        begin
          run_browser(browser_spec, block)
        rescue => error
          type = browser_spec.match(/browser\": \"(.*)\", /)[1]
          version = browser_spec.match(/browser-version\": \"(.*)\",/)[1]
          errors < type, :version => version, :error => error}
        end
      end
      message = ""
      errors.each_with_index do |error, index|
        message +="\t[#{index+1}]: #{error[:error].message} occurred in #{error[:browser]}, version #{error[:version]}\n"
      end
      assert_equal 0, errors.length, "Expected zero failures or errors, but got #{errors.length}\n #{message}"
    else
      run_browser(browsers[0], block)
    end
  end

  def run_browser(browser_spec, block)
    browser = Selenium::Client::Driver.new(
                                           :host => selenium_rc_url,
                                           :port => 4444,
                                           :browser => browser_spec,
                                           :url => test_url,
                                           :timeout_in_second => 120)
    browser.start_new_browser_session
    begin
      block.call(browser)
    ensure
      browser.close_current_browser_session
    end
  end

  def test_basic_walkthrough
    run_in_all_browsers do |browser|
      browser.open '/'
      assert_equal 'Hosted Ruby/Rails metrics - Caliper', browser.title
      assert browser.text?('Recently Generated Metrics')

      browser.click "css=#projects a:contains('Projects')", :wait_for => :page
      assert browser.text?('Browse Projects')

      browser.click "css=#add-project a:contains('Add Project')", :wait_for => :page
      assert browser.text?('Add Project')

      browser.type 'repo','git://github.com/sinatra/sinatra.git'
      browser.click "css=#submit-project", :wait_for => :page
      assert browser.text?('sinatra/sinatra')
      browser.wait_for_element "css=#hotspots-summary"
      assert browser.text?('View full Hot Spots report')
    end
  end

  def test_generate_new_metrics
    run_in_all_browsers do |browser|
      browser.open '/'
      browser.click "css=#add-project a:contains('Add Project')", :wait_for => :page
      assert browser.text?('Add Project')

      browser.type 'repo','git://github.com/sinatra/sinatra.git'
      browser.click "css=#submit-project", :wait_for => :page
      assert browser.text?('sinatra/sinatra')

      browser.click "css=#fetch"
      browser.wait_for_page
      assert browser.text?('sinatra/sinatra')
    end
  end

end

view this gist

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Written by DanM

April 8, 2010 at 10:07 am

2 Responses

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  1. The intro to your post reminded of an email thread I posted to the selenium users group. Maybe you'll find it interesting: http://groups.google.com/group/selenium-users/bro

    Right now I am giving capybara on a shot, but I'm hoping the webrat/capybara merger happens soon so things are less muddy. Speed is a concern for these tests, but also I'm finding that I was writing too many of them. I've decided to shift gears and write more model/controller/helper tests and less integration tests. If I still need speed after that, I'll be sure to refer back to this post. Thanks!

    Darren Hinderer

    April 8, 2010 at 2:04 pm

  2. Yeah it is unfortunate how hard it is to find out good information about how to best use selenium with rails. It looks like selenium-client and Webrat/Capybara are the way to go. seleniun-on-rails plugin has some serious limitations and isn't being maintained. I also agree about limiting the number of full stack tests, it is good to know a few mainline cases work, but all edge cases are better tested at the model/controller level.

    danmayer

    April 8, 2010 at 7:27 pm


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