Nowadays most computers come with more than one processor. And so it makes sense to use the additional processing power to speed up your tests by distributing them across the available processors.
One tool that helps with this is Hydra. It allows you to distribute tests across multiple processors and machines, and currently supports the Test::Unit, Cucumber, and RSpec frameworks. In this article I will focus on running Cucumber tests on a single machine.
As Hydra is distributed as a Ruby Gem its installation is pretty simple:
gem install hydra
After that, you have to add Hydra to the Rakefile of the respective project. And you have to specify the Cucumber task and the files it should use.
# Rakefile require 'hydra' require 'hydra/tasks' Hydra::TestTask.new('hydra:cucumber') do |t| t.add_files 'features/**/*.feature' end
As last step you have to create a “hydra.yml” file in the “config” folder of your project. Here you define whether the tests should run locally, and how many runners Hydra should start. Runners correspond to processors, and so the setting below is for a dual core machine.
# config/hydra.yml workers: - type: local runners: 2
With everything set up, you can now run the tests with the following command:
$ RAILS_ENV=test rake hydra:cucumber
To verify whether there is really a speed gain when running the tests in this way you have to do some kind of a benchmark (see the example below), because running something on multiple processors doesn’t necessarily mean it is faster…
For my (unscientific) benchmark I ran my test suite (consisting of 12 files with 43 scenarios and 193 steps) with the following commands five times and averaged the results:
$ time cucumber features $ time rake cucumber $ time RAILS_ENV=test rake hydra:cucumber
In the first scenario I ran the benchmark with no other user applications running, i.e. both processors were available for the task at hand. From the results you can see that using Hydra in such a scenario is the fastest solution.
cucumber: 24.1s cucumber with rake: 31.4s hydra:cucumber: 22.4s
In the second scenario I ran the benchmark in a typical development environment with many open applications, i.e. around 1.5 processors were available. This time, using Hydra is not the fastest solution, the overhead is bigger than the speed gain from having more than one processor .
cucumber: 25.9s cucumber with rake: 34.3s hydra:cucumber: 30.6s