Ensure does not overwrite existing bourbon installation.

features/generate.feature

@@ -1,6 +1,6 @@
+@disable-bundler
 Feature: Generate bourbon files via gem subcommand
 
-  @disable-bundler
   Scenario: Run `bourbon generate`
     Given I set up bourbon
     When I generate bourbon files
@@ -10,3 +10,9 @@ Feature: Generate bourbon files via gem subcommand
       | bourbon/lib       |
     And the master bourbon partial should have been generated
     And the lib files should have been generated
+    And the output should contain "Bourbon files generated to bourbon/"
+
+  Scenario: Generator does not overwrite an existing bourbon directory
+    Given bourbon is already generated
+    When I generate bourbon files
+    Then the output should contain "Bourbon files already generated, doing nothing."

features/step_definitions/bourbon_steps.rb

@@ -1,10 +1,14 @@
+Given /^bourbon is already generated$/ do
+  set_up_bourbon_directory
+  generate_bourbon
+end
+
 When /^I set up bourbon$/ do
-  write_file("Gemfile", "gem 'bourbon', :path => '../../..'")
-  run_simple("bundle install")
+  set_up_bourbon_directory
 end
 
 When /^I generate bourbon files$/ do
-  run_simple("bundle exec bourbon generate")
+  generate_bourbon
 end
 
 Then /^the sass directories should have been generated$/ do

features/support/bourbon_support.rb

@@ -0,0 +1,12 @@
+module BourbonSupport
+  def set_up_bourbon_directory
+    write_file("Gemfile", "gem 'bourbon', :path => '../../..'")
+    run_simple("bundle install")
+  end
+
+  def generate_bourbon
+    run_simple("bundle exec bourbon generate")
+  end
+end
+
+World(BourbonSupport)