ariejan de vroom

Testing $HOME with Cucumber and Aruba

15 April 2014

Cucumber and Aruba are awesome tools to write acceptance tests for your command line application. The allow you to do things like this:

Scenario: Exit with 0 when no examples are run
  Given a file named "a_no_examples_spec.rb" with:
    """ruby
    """
  When I run `rspec a_no_examples_spec.rb`
  Then the exit status should be 0
  And the output should contain "0 examples"

This example was taken rspec-core.

Aruba basically does three things for you:

The problem

Now, if you are writing a CLI that interacts with a configuration file in the user’s home directory, you’d write a cucumber like this:

Scenario: use .my-app configuration
  Given a file named "~/.my-app" with:
    """
    awesome_enabled: true
    """
  When I run `my-app`
  Then the output should contain "AWESOME"

But how does your app and Aruba differentiate between this generated test file and your actual configration file in your home directory? It doens’t.

The answer

The solution is quite easy and elegant, in your Before set the $HOME environment variable to a custom location inside the tmp/aruba directory.

In features/support/env.rb:

Before do
  set_env 'HOME', File.expand_path(File.join(current_dir, 'home'))
  FileUtils.mkdir_p ENV['HOME']
end

This will set $HOME to tmp/aruba/home in the context of your cucumbers (and execute binary). current_dir automatically points to the right location for the aruba temporary directory.