domain_steps.rb

# Some handy-dandy sub-domain steps for use with Capybara if you're using SubdomainFu

def get_base_url
  # NOTE: I'm defining SITE_URL higher up somewhere. You might want to change that piece.
  base_url = SITE_URL.split('.').reject { |piece| SubdomainFu.mirrors.include? piece }.join('.')
end

When /^(?:|I )visit (.+) for the subdomain "([^\"]*)"$/ do |new_path, subdomain|
  new_url = get_base_url
  new_url = subdomain + "." + new_url if subdomain.present?

  host! new_url
  Capybara.default_host = host

  When "I visit #{new_path}"
end

Then /^(?:|I )should land on the subdomain "([^\"]*)"$/ do |subdomain|
  current_host = URI.parse(current_url).host
  if current_host.respond_to? :should
    current_host.should match /^#{subdomain}/
  else
    assert_match /^#{subdomain}/, current_host
  end
end

Then /^(?:|I )should not land on the subdomain "([^\"]*)"$/ do |subdomain|
  current_host = URI.parse(current_url).host
  if current_host.respond_to? :should
    current_host.should_not match /^#{subdomain}/
  else
    assert_no_match /^#{subdomain}/, current_host
  end
end

Then /^(?:|I )should land on the standard subdomain$/ do
  current_host = URI.parse(current_url).host
  domain_regex = (SubdomainFu.preferred_mirror.blank?) ? /^#{get_base_url}$/ : /^#{SubdomainFu.preferred_mirror}/
  
  if current_host.respond_to? :should
    current_host.should match domain_regex
  else
    assert_match domain_regex, current_host
  end
end

env.rb

SITE_URL = "www.example.com"

# Make sure you reset your host at the start of each test!

Before do
  host! SITE_URL
  Capybara.default_host = host
end

subdomain.feature

Feature: Subdomain checks

  Scenario: Visiting a specific login page
    Given I am not logged in
    When I visit the login page for the subdomain "foo"
    Then I should land on the subdomain "foo"
    And I should be on the login page
    # extra stuff here...